24. The anatomy and histology of the spleen. Differentiation of the ectoderm.

24. The anatomy+ histology of the spleen. Differentiation of the ectoderm.

* Completely Intraperitoneal, except at the hilum, where splenic vessels enter/ exit, part of FOREGUT

Anatomy of Spleen:

General Info:

• Ovoid, usually purplish, pulpy mass about the size+ shape of one’s fist.
• Largest of the lymphatic organs
• Spleen varies in size, weight+ shape, it is usually app. 12 cm long+ 7 cm wide
• It participate in the body defense system as a site of lymphocyte(white blood cell) proliferation+ of immune surveillance+ response.
• PRENATALLY= a hematopoietic organ
• After birth = is involved in identifying, removing + destroying expanded red blood cells+ broken- down platelets, in recycling iron+ globin. S
• serves as a blood reservoir
• storing RBC+ platelets+ to a limited degree
• can provide a sort of”self transfusion” as a response to the stress imposed by hemorrhage.

Location: Located in the left upper abdominal quadrant or hypochondrium, where it receives the protection of the lower thoracsic cage

Surface Projection:

• b/w 8th & lower border of 11th rib,
• Ant = tip of 11th L rib,
• Post = 2 finger medial to L inguinal line,
• Long axis runs along the post part of 10th rib

Topography: 2 main surfaces – Costal & Visceral

• Costal – contact w/ rib cage & diaphragm
  • In the costal region, it rests on the colic flexure
  • associated post w/ 9-11 th ribs+ separated from them by the diaphragm+ the costodiaphragmatic recess
• Visceral – contact w/ abdominal organs = impressions made by them
  • Gastric – ant/med, fundus of stomach
  • Renal – behind, L kidney
  • Colic – below, L Colic flexure of LI
  • Hilum – splenic branches of the splenic artery+ vein enter+ leave, SPLENIC HILUM often in contact with the tail of the PANCREAS, L boundary of the omental bursa.

Function: Hemopoetic function or Immune System function

• Primary Functions:
  • produces lymphocytes & antibodies
  • phagocytosis of damaged blood cells
  • storage of blood cells
  • proliferation of lymphocytes
  • formation of blood cells in fetal life
  • removal of macromolecular antigens from blood
  • retrieval of Fe from RBC Hemoglobin
• Secondary Functions:
  • Antigen presentation by APCs = immune response
  • Activation and proliferation of B & T cells
  • differentiation of B cells and plasma cells
  • secretion of antibodies on white pulp
  • blood storage

Blood Supply:

• The SPLENIC Artery is the largest branch of the celiac trunk+ follows a tortuous course
  • post to the omental bursa
  • ant to the left kidney+ along the sup. border of the pancreas.
• SPLENIC VEIN: is formed by several tributaries that emerge from the hilum.
  • It is joined by the Inf Mesenteric v & runs post. to the body+ tail of the pancreas throughout most of its course.
  • The splenic vein unites with the Sup mesenteric v post. to the neck of the pancreas, to form the PORTAL VEIN.

Lymph Drainage: The splenic lymphatic vessels leave the lymph nodes in the splenic hilum+ pass along the splenic vessels to the pancreaticosplenic lymph nodes.

Innervation: The nerves of the spleen, derived from the celiac nerve plexus, are distributed mainly along branches of the splenic artery+ are vasomotor in function.

Peritoneal relations: Spleen is a soft, vascular(sinusoidal) mass with a FIBROELASTIC CAPSULE, entirely surrounded by peritoneum except at the SPLENIC HILUM. These ligaments, containing splenic vessels, are attached to the hilum of the spleen, on its medial aspect

• Gastrosplenic lig (ant) – connects spleen to greater curve of stomach, spleen contacts the post. wall of the stomach+ is connected to its greater curvature by the GASTROSPLENIC lig
• Phrenicolieanal lig (post)
• Lienorenal lig – * If tail of pancreas is retroperitoneal, then inf gastrophrenic lig forms pancreaticolienal ligament & carries splenic a/v –> spleen, Inf border of phrenico lienal extends –> L colic flxure = phrenicocolic lig, and supports spleen inferiorly = nest of spleen

CLINICAL NOTE – frequently ruptured by fractured ribs & repair difficult, may be removed surgically w/ minimal  effect on body function –> function assumed by other reticuloendthelial organs, like Liver.

Histology of Spleen:

Slide #24 Spleen * H&E

Structures to Identify:

• red pulp
• white pulp
• lymphatic follicles
• germinal center
• central a
• trabecular v
• venous sinuses

General Info:

• largest lymph organ, on L side of Ab cavity
• The spleen contains a large quantity of blood, that is expelled periodically into the circulation by the action of the smooth muscle in its capsule+ trabeculae.
• thin fibrous capsule of the spleen
  • is composed of dense, irregular, fibroelastic CT.
  • fibrous capsule is thickened at the splenic hilum
  • divides spleen into compartments called splenic pulp
  • made of collagen w/ myofibroblasts
• CT trabeculae, arising from the deep aspect of the capsule,
  • carry blood vessels to+ from parenchyma or splenic pulp, the substance of the spleen.
  • round or nodular and may contain a/v = trabecular a/v
    

• White Pulp – site of lymphatic nodules
• Red Pulp – site of sinues and cords

NOTE: PALS = T lymphocytes, Nodules = B lymphocytes

White Pulp – lymphatic nodules with germinal center around a central artery

The spleen is characterized by numerous aggregation of lymphatic nodules. These nodules constitute the white pulp of the organ.The lymphatic nodules also contain, GERMINAL CENTERS, that decrease in no. with age. NO distict cortex+ a medulla, as seen in lymph nodes. NO subcapsular or trabecular sinuses. The capsule+ trabeculae in the spleen are thicker than those around the lymph nodes+ contain some smooth muscle cells. The large lymphatic nodules =  white pulp of the spleen. Each nodule normally exhibits a peripheral zone with densely packed small lymphocytes = the peri-arterial lymphatic sheeth = PALS, aka Thymus dependent zone,

The central artery, in the lymphatic nodule, has a peripheral or an eccenteric position. Because the artery occupies the center of the periarterial lymphatic sheath, it is called the central artery. The cells found in the periarterial lymphatic sheath are mainly T cells. A germinal center may not always be present. In the more lightly stained germinal center are found B cells, many medium- sized lymphocytes, some small lymphocytes+ lymphoblasts.

• White pulp is the side of immune response to bloodborne antigens
• T cells surround the central arteries,
• Whereas B cells are mainly in the lymphatic nodules
• Antigen- presenting cells + macrophages are found in the white pulp.
• Passing through each lymphatic nodule is a blood vessel called a CENTRAL ARTERY, that is located in the periphery of the lymphatic nodules.
  • Central arteries are branches of trabecular arteries,
  • become ensheathed with lymphatic tissue
  • between the venous sinuses+ form a spongy meshwork of reticular CT
  • usually obscured by the density of other tissue.

Red Pulp – consists of splenic cords+ splenic(blood) sinusoids

The red pulp contains the SPLENIC CORDS+ VENOUS SINUSES that course between the cords. These represent the branches of the central artery after it leaves the lymphatic nodule. Capillaries+ pulp veins are also present.

• Splenic cords of Billtoth
  
  • Splenic cords are thin aggregation of lymphatic tissue containing small lymphocytes, associated cells+ various blood vessels.
  • loose meshwork of reticular cells & fibers w/ high # of RBCs
  • contain macrophages, lymphocytes, plasma cells, granulocytes, & enterocytes
• Splenic sinuses
  • are dilated vessels lined with modified endothelium of rod shaped cells that appear cuboidal in transverse sections.
  • Endothelium has longitudinal axis parallel to direction of vessels
  • prominent IC spaces
  • no continuous basal lamina & wraps loops around sinuses (perpendicular to long axis)
  • mostly washed out due to increased # of RBCs
• Also present in the red pulp are the pulp arteries.
  • surrounded by PAMS –  Peri-Arteriolar Macrophage sheath – macrophages w/ hemosiderin pigment granules
• CT trabeculae with trabecular artery+ trabecular vein are evident
  • These vessels have endothelial tunica intima+ muscular tunica media
  • tunica adventitia is not apparent because the CT of the trabeculae surrounds the tunica media.

Arterial Flow:

Central a  (white pulp) –> branches –> marginal sinus –> red pulp –> straight arterioles –> pericellular arterioles –> arterial capillaries –> empty directly into the reticular meshwork of spleen –> splenic sinuses & cords of red pulp –> blodd exposed to macrophages (in sheathed arterioles, arterile capilaries) –> squeeze through walls of splenic sinus = Open circulation

Venous Flow:

Blood collected in sinuses –> tributaries of trabecular v –> larger v –> splenic v –> joins sup/inf mesenteric v –> hepatic portal v.

Embryology of Spleen:

• Develops from mesoderm, w/in dorsal mesogastrium
• development starts w/in the 5th week
• spleen appears as proliferation of mesoderm
• with the rotation of mesogastrium, goes into the post side of the abdomen
• remains intraperitoneal
• supported by lienogastric (to greater curve of stomach) and lienorenal lig (to L kidney)
• Mesenchymal cells in the developing spleen differentiate to form the capsule, trabeculae, and reticular framework.
• Development involves establishment of mesenchymal trabeculae within a blood vascular network consisting of a large number of endothelial sinuses.

Embryology- Differentiation of Ectoderm:

• Ectoderm is one of the three layers of the trilaminar germ disk
• Cells remaining in the epiblast after endoderm and mesoderm are produced = ectoderm
• @ beg of 3rd week, the ectoderm layer has shape of disk that is broader towards the head (cranial portion), than the tail end(caudal).
  
• After notochord and prechordal mesoderm form, these cause ectoderm on top of them to thicken and form neural plate
• Cells of neural plate = neuroectoderm — process = neuralation
• From Wikipedia:
  Generally speaking, the ectoderm differentiates to form the nervous system, epidermis, and the outer part of integument.

  In vertebrates, the ectoderm has three parts: external ectoderm (also known as surface ectoderm), the neural crest, and neural tube. The latter two are known as neuroectoderm.

23. Anatomy, Histology, & Embryology of the Pancreas

*Pancreas is secondary retroperitoneal, with the exception of the tail, the foregut.

Anatomy of Pancreas

• Location: Within the curve of the duodenum, located in the epigastric and left hypochondriac regions

• Surface Projection: Surface projection of is different depending on the part of it, and will be entailed later.

• Topography: touches the doudenum, the spleen, the left kidney, the lower border of the stomach.

• Function: releases secretions in an exocrine fashion, namely pancreatic juice, which it then secretes into the duodenum through the major duodenal papilla, or papilla of Vater. This major pancreatic duct is also called the duct of Wirsung. Endocrine secretions include glucagon and insulin into the blood.

• Parts:

  • Head – located between L1-2 in curve of the duodenum, to the descending and horizontal parts of it. develops mainly from the ventral pancreatic bud, except the upper part, which is from the dorsal pancreatic bud. Is located right to the sup mesenteric a/v.SP = head of pancreas is anterior loc to IVC, right renal a/v, left renal v Uncinate process– at lower head behind sup mesenteric a/v
  • Neck – short, 1-2cm, sup mesenteric a/v go behind the neck, @ notch below neck, called pancreatic notch. Ant surface of neck covered with peritoneum, and moves along with movements of pylorus of stomach. Sup mesenteric v and splenic v combine behind the neck of pancreas, to form portal v.
  • Body – loc @ L1-2, in front of vert column, posterior to lesser sac Has 3 surfaces:
  • • Ant – covered by peritoneum, and indirectly contacts post stomach, lies in floor of lesser sac, helps form gastric bed >
    • Post – contact with aorta, sup mesenteric a/v, L kidney & renal vessels, and L suprarenal gland, Splenic a runs in tortous path superior to it, and has groove for splenic v.
    • Inf – touches 3rd and 4th part of duod Omental tuberosity – in sup surface of body below celiac trunk, contact with visceral surface of liver. (T12-L1 midline)
  • Tail – loc. at left costal arch, 2-3 fingers lat to T12, runs to hilum of spleen.
    • Can be retroperitoneal or intraperitoneal.
    • If shorter, than usually retroperitoneal, like the rest of pancreas. Then a small peritoneal ligament = pancreaticolineal lig extends from tip of tail –> hilum of spleem. Splenic a/v enter spleen through this ligament.
    • If longer, intraperitoneal, and splenic a/v can go directly to spleen.
  • Ducts:
    • Main pancreatic duct = Duct of Wirsung, duct of ventral pancreatic bud, begins in tail and runs along entire pancreas, till head, where it turns inf and runs with common bile duct. Opens at major duodenal duct – Ampulla of Vater, which is gaurded by sphincter of Oddi, after joining bile duct.
    • Accessory pancreatic duct = Santorini’s duct can open into main or minor duodenal papilla, sometimes both. minor duodenal papilla located 2cm above major one, Begins in lower portion of the head, and drains small portion of head and body.
    • Clinical NOTE – Bile ducts is embedded into a groove on the post/sup side of the head. If tumors are located within the head, this can block bile flow into the duodenum, resulting in jaundice.
• Blood Supply: B/c develops from FOREGUT – supplied by branches of celiac trunk.
  • Splenic a – supplies derivatives of dorsal pancreatic bud –> neck, body, tail of pancreas located on shallow groove on sup/post side of pancreas. 10 branches, that can form arterial arcades (networks) with branches from gastroduodenal a and sup mesenteric a
  • Sup pancreaticoduodenal a (gastroduodenal a) & Inf pancreaticoduodenal a (sup mesenteric a ) splits into ant/post branches to supply the head of the pancreas
  • Most veins empty into splenic v, which is embedded into the back of the pancreas itself

• Lymph Drainage
  • lymph vessels follow the arteries and drain into pancreatiosplenic nodes that lie along splenic arteries. The ones by the head go to pyloric lymph nodes, as well.
  • These two sets of nodes drain into celiac, hepatic, and sup mesenteric lymph nodes

• Innervation
  • PNS – (+) digestion, secretion, vasodilation.
    • From CN X, carries pre ggl fibers to submucosal and myenteric plexus within walls of organs, with short post ggl PNS fibers.
    • Go to parenchyme (acinar cells and islets of Langerhans)
    • Inc Insulin secretion, Inc glucagon secretion
  • SNS – (-) digestion, secretion, vasoconstriction
    • SNS –> (T5-T9) from thoracic splanchnic n –> aortic hiatus –> celiac ggl plexus around the celiac trunk –> post ggl fibers run with branches of celiac trunk.
    • Go to pancreatic glands and parenchyme (pancreatic acinar cells and islets of Langerhans)
    • dec insulin secretion, inc glucagon secretion

Peritoneal ligaments:Peritoneal ligaments: none ,except for the tail sometimes, which can be located with in the pancreaticolienal ligament.

Histology Pancreas slide # 59 *H&E

Structures to Identify:

• intercalated duct

• intralobular duct

• a/v/capillaries

• Islets of Langerhans

• Secretory acinus

• A,B,D, cells

• CT septa lobules

General Information

• Digestive gland with head, neck, body , tail regions

• Mixed gland with endocrine and exocrine functions

Exocrine:

• Tubuloacinar glands manily composed of serous secretory units

• Secretions proteolytic enzymes

• Proteolytic Endo-peptidases: trypsinogen, chemotrypsinogen

• Exopeptidases: procarboxypeptidases, proaminopeptidases, alpha amylases, lipases nucleolytic enzymes

• Has hormonal/ neural control regulation: Secretin – inc. fluid secretion, CCK – pro enzyme secretion Chyme of stomach and duodenum stimulate enteroendocrine cells to secrete CCk and Secretin → causes pancreas to secrete

• Forms most of pancreas, has tightly packed serous acini – circular gland, small circular lumen, darkly stained. zymogen cells arranged in lobule fashion

• Lobules seperated by thin intralobular, and interlobular CT septa – have blood vessels, interlobular ducts, pacinian corpsucles

• Pacinian corpsucle – concentric circles, lighter than surrounding acini, is a sensory receptor

Endocrine:

• Islets of Langerhans (Pancreatic Islets) – highly vascularized epitheloid tissue

• alpha, beta, delta, cells in periphery, beta cells also in center.

• light staining, globular, with thin CT capsule surrounding it.

• Pyramid shaped cells facing central lumen,

• Secretions go to large vacular network of capillaries just outside the islets,

• Excretes into intercalated duct, lined by low cuboidal epithelium

Alpha cells – glucagon – inc amount of glucose in blood

Beta cells – insulin – dec amount of glucose in blood

Delta cells -Somatostatin – inhibits the other two

Duct flow:

Within the islets, flow into pale staining centro acinar cells within lumen → intercalated (same as intralobular) ducts → interlobular ducts (simple cuboidal epith) in interlobular CT septa → larger ducts ( also interlobular, but with stratified columnar epith)

Embryology – Development of Pancreas

• Endodermal lining of forgut forms two outgrowths, ventral pancreatic bud and dorsal pancreatic bud

• Within both buds, endodermal tubules surr. by mesoderm –> branch to from acinar cells and ducts (exocrine part).

• Clumps of cells within exocrine part form, and become the future islets (endocrine part)

• Remember how the duodenum rotates 90 degrees clockwise? Because of this, the ventral bud (ant) rotates also – dorsally (post) and fuses with the dorsal bud already there to form adult pancreas

• Ventral bud = uncinate process and lower part of head of pancreas

• Dorsal bud = rest of pancreas

• Main pancreatic duct (of Wirsung) = formed by distal dorsal bud and all of ventral bud

• Acc pancreatic duct (of Santorini) = prox part of dorsal bud

• Endoderm origin = acinar cells, islet cells, simple columnar and cuboidal lined parts of duct system

• Visceral mesoderm = CT surrounding them, and a/v/capillaries

Anim : http://www.mcb.harvard.edu/melton/animation.html

22. The anatomy, histology and development of the liver and biliary ducts and gallbladder.

*Liver is intraperitoneal, except for bare area, and has FOREGUT origin

Anatomy of Liver

• General Info
  • largest gland in the body and largest organ(after skin)
  • weighs app. 1500 g; 2.5 % of adult body weight
  • in late fetus: twice as large( 5% of body weight)
• Location
  • lies mainly in the right upper quadrant of the abdomen
    
  • hidden and protected by the thoracic cage and diaphragm
  • normal liver lies deep to ribs 7-11 on the right side and crosses the midline towards the left nipple.
    
  • L. occupies most of the right hypochondrium, the upper epigastrium and extends into the left hypochondrium
  • inf to the diaphragm, which separate it from the pleura, lungs, pericardium and heart
• Function
  • all nutrition absorbed from the gastrointestinal tract are initially conveyed first to the liver by the portal venous system(except for fat)
  • metabolic activities, glycogen storage and secretion of bile,
  • degrade or conjugate toxic substances to render them harmless
  • Protein synthesis
  • Heparin production
  • Breakdown of Hemoglobin
  • Hematopoiesis = RBC production
  • Storage of vitamins, Fe, and Cu
  • Bile function:
    • bile passes from the liver via the biliary ducts
    • R & L Hepatic ducts, join to form the common bile duct, which unite to form the cystic duct to form the bile duct
    • the liver produces bile continuously,
      
    • between meals it accumulates and is stored in the gallbladder, which also concentrates the bile by absorbing water and salts.
    • when food arrives in the duodenum, the gallbladder sends concentrated bile through the bile ducts to the duodenum

• Surface Projection
  • Upper border = 5th rib @ mid inguinal line
  • Lower border = @ ant axillary line –> midinguinal line, follows the R costal arch, then @ end of 10th, asc obliquely into epigastrium, crosses midline @ transpyloric line, @ 8th L rib, enters hypochondrium
  • Lower and upper border meet jsut medial to L midinguinal line
• Topography
  • 2 surfaces = diaphragmatic, and visceral.
  • the diaphragmatic surface of the liver is smooth and dome shaped, where it is related to the concavity of the inf surface of the diaphragm

  • Impressions on the visceral surface:

    1) gastric + pyloric areas: right side of the ant. aspect of the stomach

    2) duodenal area: sup. part of the duodenum

    3) lesser omentum: extends into the fissure for the ligamentum venosum

    4) fossa for gallbladder

    5) colic area: right colic flexure + right transverse colon

    6) renal+ suprarenal areas: right kidney + suprarenal gland

• Parts
  • separated into R & L lobe ant by falciform ligament (a fold of peritoneum that attaches the liver to ant ab wall)
  • (post) – split into 4 lobes by a number of structures that make a “H” pattern on the visceral surface
    • 4 lobes are : R, L, caudate, and quadrate. (quadrate functionally part of L lobe, and caudate functionally part of both)
    • H made up of R and L sagittal fissures & transverse limb:
      • R-ant = fossa of gallbladder (sits on quadrate)
      • R-post = IVC fossa
      • L ant = falciform and round ligament
      • L post = ligamentum venosum, and hepatogastric lig.
      • Transverse limb = Porta Hepatis = ( portal vein, hapatic artery + lymphatic vessels+ hepatic nerve plexus+ hepatic ducts that supply + drain the liver enter and leave it.
    • Round ligament = remnant of umbilical v., @ inf free edge of falciform ligament
    • Ligamentum venosum = remnant of Ductus venosus, which shunts a significant majority (80%) of the blood flow of the umbilical vein directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver.
• Peritoneal Relations of Liver
• • subphrenic recesses: sup. extensions of the peritoneal cavity(greater sac) exists between diaphragm + ant. + sup. aspects of the diaphragmatic surface of the liver
    • seperated into right and left recesses by the falciform ligament
  • suphepatic space= portion of the supracolic compartment of the peritoneal cavity immediately inf. to the liver
  • hepatorenal recess= posterosuperior extension of the suphepatis space, lying between the right part of the visceral surface of the liver and kidney/ suprarenal gland
    • cavity- deepest part(deepest next to rectovesical pouch) in supine position, fluid draining from the omental bursa flows into this recess.
    • communicates ant. with the right subphrenic recess
    

    Recesses of Liver

    

    Ligaments of Liver

  • bare area of liver: diaphragmatic surface is covered with visceral peritoneum, except there.
    • It lies in direct contact with the diaphragm.
    • is demarcated by the reflection of peritoneum from the diaphragm to it as the ant(upper) + post(lower) layers of the coronary ligament.
  • Right triangular ligament: end  of coronary lig on R side
  • Left triangular ligament: end of coronary lig of L side
  • Hepatogastric ligament
  • Hepatorenal ligament
  • Hepatoduodenal ligament = remnant of ventral mesoduodenum, connect portal v. and duodenal cap
  • Hepatogastric and hepatoduodenal ligament together make up the borders of epilploic (omental) foramen, that leads from greater sac to lesser sac (behind the stomach), some say it also makes up the lesser omentum
  • ventral mesogastrium – liver develops in this, and the liver divides it into two ligaments: the lesser omentum & falciform ligament.
    
  • Bare area – no peritoneal coverage. Borders on both sides is falciform ligament, anterior and posterior leaf of coronary ligament, triangular ligament where ant/post leaves of coronary ligament unite. *Location of where hepatic v enter IVC
• Blood Supply
  • receives O2  blood from hepatic a
  • have many many many variations
    
  • de-O2, nutrient rich, poss toxic blood –> portal v (portal v discussion another topic, please look at that one)
    
  • Hepatic a proper –>ascends in hepatoduodenal lig (R edge of lesser omentum) splits into R and L Hepatic a, R hepatic gives cystic a, Hepatic a immediately split into segmental branches
    • R Hepatic = R lobe, R 1/2 of caudate lobe
    • L Hepatic = L lobe, quadrate lobe, L 1/2 of caudate lobe
  • Hepatic v – drains blood of liver, usually 3 of them, Sinusoids of liver –> bigger br –> hepatic v –> IVC (@ bare area)
• Lymph supply
  • Liver is major lymph producing organ
  • Superficial lymph nodes
    • in fibrous capsule of liver, just below the peritoneum
      
  • Deep lymph nodes
    • in CT with portal triads and hepatic v.
  • Superficial  l.n.  from ant diaphragmatic and visceral surface, and deep lymph vessels from around portal triads –> hepatic nodes, along hepatic vessels and ducts in lesser omentum–> celiac nodes –> cisterna chili
  • Superficial l.n. from post diaphragmatic and visceral surface –> bare area of liver –> phrenic nodes, a or to lymph nodes with hepatic v to IVC, thru diaphragm –>  post mediastinal nodes –> R lymph/thoracic duct
  • lymph can also go –>  L gastric, parasternal, and from round ligament area, umbilical nodes.
• Innervation
  • hepatic n plexus @ porta hepatis, these branches come from the celiac plexus which sits around the celiac trunk
  • SNS = from celiac plexus
  • PNS = ant/post vagal trunks
  • N fibers run with arteries

Biliary Ducts & Gall Bladder

*Intraperitoneal, part of foregut

Gallbladder

• Location
  • Jxn of R 9th CC and lat border of rectus abdominus  where midinguinal line crosses 10th rib (fundus of it)
• General Info/Topography
  • Pear shaped sac on inf surface of liver in fossa b/wR lobe and quadrate lobe.
  • lies right next to the 1st/2nd part of  diaphragm
  • touches transverse part of colon
• SP = above, can only be palpated if gallstone present * made of calcifications of cholesterol and/or bilirubin. Gallstones more common in women than men, especially those with multiple pregnancies and/or overweight, and older.
• Function
  • receives and stores bile and concentrated by absorbing H20 and salts and stores it
  • contracts to expel bile via (+) by CCK, which is produced by duodenal mucosa when food arrives there
  • Bile used to breakdown fat and fat soluble vitamins
• Parts
  • Fundus – wide end, projects from the inf border of liver, located at tip of right 9th CC
  • Body – on visceral surface of liver, in GB fossa
  • Neck – narrow, tapered and runs towards porta hepatic, location of cystic duct
• Blood Supply
  • primarily cystic a, from R Hepatic a
  • cystic v
    
    • from the biliary ducts and neck of gallbladder –> portal v, joins v from hepatic ducts and upper bile duct
    • from fundus and body –> visceral surface of liver –> hepatic sinusoids
• Lymph Drainage
  • cystic lymph nodes –> hepatic lymph nodes –> celiac lymph nodes
• Innervation
  • SS = R phrenic n
  • SNS = celiac plexus
  • PNS = CN X
  • fibers run with cystic a.

Biliary System:

• Bile is made in Liver and stored in gallbladder. Bile is released into the duodenum when food arrives, and therefore fat needs to be broken down. Hepatocytes  secrete bile into bile canaliculi in b/w them.
• Bile canaliculi unite to from intrahepatic bile ducts, that lie in portal triads with the hepatic portal v and hepatic arteries.
• Bile ductules combine to form R and L Hepatic ducts
• R & L Hepat ducts combine to form  Common Hepatic Duct
• Cystic duct to gall bladder is from common hepatic duct
  • have spiral valves (Heister’s valves) which keep duct open si if common bile duct closed, bile –> cystic duct –> GB
• Common Hepatic + Cystic duct = Common bile duct
  • 10 cm long and 1 cm in diameter
  • lies in b.w hepatic a and portal v
  • ususally embedded into post. surface of the head of the pancreas.
  • Left side of the desending part of the duodenum, the bile duct comes into contact with the main pancreatic duct.
  • These ducts run oblique through the wall of this part of the duodenum, where they unite to form the hepatopancreatic ampulla, the dilation within the major duodenal papilla.
  • distal end of ampulla opens into great duodenal papilla (about 1/3 way down descending part of duodenum, also called papilla of Vater, or Greater Duodenal papilla)
• Sphincter of Oddi holds the opening of the papilla closed  – there are three parts to it, forming a sphincter for the bile duct, pancreatic duct, and for the papilla itself. PNS activity opens it.

Histology of Liver and Gallbladder

#57 Pig Liver * H&E

Structures to Identify:

• Fxn’l lobule
• central v
• Bile duct
• hepatic a
• portal v
• CT septa
• lymph nodule
• sinusoids
• bile canaliculi
• Kupffer cells
• Glisson’s capsule
• Hepatocytes (parenchyme)

Low power magnification: you see the lobular patternof the human liver, but less CT than for pic liver. Pig liver shows hepatic lobules the best b/c of prominent CT septa invaginating from surrounding Glisson’s capsule.

Medium power magnification:  hepatic lobules containing the central vein are dermacated by narrow stripes of interlobular CT made of reticular fibers.

Organization of Hepatic Lobules:

• Functional units of the liver, described as lobules or acini, are made up of irregular interconnecting sheets of hepatocytes seperated from one another by the blood sinusoids.
• parenchyme of liver is hepatocyte – normally 2 layers with sinusoids in b/w
• Sinusoids convery mixed blood of Liver –> drain into central v.
  
• radiating from central v –> periphery of lobule = plates of hepatic cells, with hepatic sinusoids in b/w, where venous and arterial blood mix
  
• Space of Disse = b/w hepatocytes basal surface (sinusoids),
  
  • Perisinisoidal space b/w endoth of sinusoids and parenchyme
  • have microville that go into space and absorb protein from sinusoids
  • contain Ito cells and hepatocytes

3 ways of describing Hepatic lobules:

• Classical lobule model – has at its center the v surrounded by  Space of Mall, (b/w CT stroma and outermost hepatocytes), sinusoids, and hepatic triad
• Portal lobule model – emphasizes exocrine fxn of liver and has bile duct in center (part of portal triad)
• Liver acinus model – best correlation among blood perfusion and metabolic activity and liver pathology
  • eliptical region between 2 central v and interlobular septum, divided into 3 zones
  • hepatic a, portal v, and bile duct from portal triad at periphery of lobules

Portal tracts contain the portal triad: with in the interlobular CT septa, each lobule has several portal triads surrounding it.

1. interlobular vein: branch of portal vein

2. interlobular artery: a branch of the proper hepatic artery, a thick- walled vessel with smaller diameter and the typical structure of arterioles or arteries

3. interlobular bile duct: ducts of variable size, lined by simple cuboidal or columnar epithelium

Cells of Liver

• Kupffer cells – belong to MPS, derived from monocytes, lie in sinusoid walls with endothelium, have pacytoic capabilites to help degrade RBCs and Fe/ferritin. In case of splenectomy, # inc to make up the difference in Hgb and RBC breakdown = see them best in RAT slide #57C, special staining required to see properly.
• Ito cells – in space of Disse, stores vit A (precursor of retinol) that is needed for proper vision.
  • Note = In pathological cases, differentiate into myofibroblasts and secrete collagen, causing  fibrosis.
    
• Hepatocytes – main parenchymal cells of liver, last 5 months, need lots of mitochondria for energy
  • polyhedral in shape
  • tight junction in b.w w/ bile canaliculi
  • peroxisomes (H2O2 –> H2O +O2)
  • Smooth ER to detox drugs
  • Endocrin fxn = secret apolipoproteins
  • lysosomes for degradation

More General Info

• Liver cells are large, polygoneal cells with round, centrally located nucleus and prominent nucleus
• Binucleate cells are seen in this section. The hepatocytes form flat, anastomosing cords;
• Sinusoids are found between the hepatic cords, the sinusoids are lined by a discontinous layer of endothelium with flattend and condensed nuclei.
• Kupffer cells are also present there, they are larger+ darker then the other cells of the sinusoids; sinusoids contain all the cellular elements of blood
• The space as a fine slit between the sinusoid lining cells + the hepatocytes(the space of disse)is at the limit of the resulution of the LM.
• Sometimes the hepatic capsule(Glisson’s capsule) is visible as a thin layer of CT, covered by simple squamous epithelium(visceral peritoneum) on the surface.
• It also contains substances that bind to metabolites in the intestine to aid absorption.
• A series of ducts of increasing diameter diameter + complexity, beginning with canaliculi between individual hepatocytes + ending with the common bile duct, deliver bile from the liver + gallbladder to the duodenum.

Endocrine v Exocrine Function

• each liver has both exocrine + endocrine functions;
  
• exocrine secretion of the liver:
  • secretes bilirubin (byproduct of  RBC breakdown produced by Kupffer cells)
  • Antibodies – produced in LP of SI/LI taken from blood by hepatocytes –> bile –> lumen of SI = control bacteria level there.
    
  • produce bile which contains conjugated+ degrated waste products that are delivered back to the intestine for disposal.
  • release up to 1L of bile to canaliculi daily
  • Bile flow:  Bile canaliculi –> bile duct –> hepatic duct –> cystic duct –> gallbladder –>cystic duct –> common bile duct –> duodenum
    
• The endocrine secretion of the liver
  • are released directly into the blood that supplies the liver cells
  • these secretions include albumin, nonimmune alpha + beta globulins, prothrombin + glycoprotins including fibronectin
  • activation of vitamin D, thyroxin, and growth hormone
    
  • Glucose (released from stored glycogen) + T3  (the more active deiodination product of thyroxine), are also released directly into the blood.

Blood Supply/Lymph Drainage w/in liver

• from portal v (spleen, stomach, pancreas, SL, LI) + hepatic a proper
• portal blood contains:
  • absorbed degrade materials from GI tract
  • blood cells from spleen
  • pancreatic endocrine secretions
• venous blood from portal v mixes with arterial blood from hepatic a proper in a 75%/25% ratio in portal capillaries
• flows within perilobular a/v
• as said perviously, blood drains into sinusoids, lined with discontinous endothelium– which allows the communication of hepatic blood with hepatocytes
• remember that blood and bile never mix, they have seperate flow channels
• Lymph –> Space of Mall, located in endothelial lining –>drain into v. –> thoracic duct

# 57A Pig Liver *AZAN

• blue = collagen
• stains CT capsule, loose CT (collagen type I and II)
• stains reticular fibers in space of Disse
• AZAN = azocarmine red, and aniline blue

#57C Rat Liver * Toluidin Blue & Nuclear fast red

• Structures to Identify: sinusoids, Kupffer cells, Endothelium cells, Hepatocytes, Bile canaliculi
• To demonstrate structures of parenchyme of liver
• Kupffer cells are clearly visible, b/c they phagocytose the dye – present in sinusoids
• Hepatocytes clearly defined
• NFR stains nuclei red
• Sometimes, bile canaliculi will be visible b/w hepatocytes

#58 Human Liver *H&E

• Structures to Identify:  portal v, bile duct, hepatic a/v, central v, parenchyme, lymph nodules
• same features as rat, but CT stroma not as prominent
• if hepatic v, present, it will be alone and not in hepatic triad

Histology of Gallbladder #56 *H&E

Structures to Identify:

• Mucosa – deep folds when GB empty
• smooth m
• glands ( only in neck region)
• Rokitansky-Aschoff sinuses
• a/v
• adventia/serosa

General Info

• concentrates and stores bile for delivery into duodenum – done by salt active transport from bile and passive movement of H2O in response to salt transport
• Bile flow = R/L Hepatic ducts –> common hepatic duct –> cystic duct –> GB–> cystic duct –> common bile dcut –> duodenal papilla of Vater

Mucosa

• characterized by tall columnar epithelium with so called  diverticuli or crypts, where the mucosa makes deep folds. LOOK FOR THESE – v. characteristic of GB = Rokitansky – Aschoff sinuses
  
  • advential invaginations of mucosal membrane
  • common site of bile stones inflammation, as these can close themselves off into closed sacs, where bacteria can collect
  • can extend into musc. layer
  • from as a result of inc pressure in GB and damage to wall of GB
• has absorption function like in SI/LI
• concentration of mitchondria found on basal/apical surfaces
• Na/K ATPases on lat cell surfaces (not seen, theory only)
• cells also have microvilli to increase surface area = absorption of H2O andminerals = concentrate bile
• LP = rich in fenestrated capillaries for absorption and lymphocytes as usual

No Submucosa or Musc Mucosa!!

Musc ext

• below LP, contains unordered smooth m layers

• • contract when activated by hormones from SI enteroendocrine cells
  • contract dec volume of GB –> bile expelled into cystic duct
• lots of elastic fibers interwoven with it
• have CT covering smooth m bundles with a/v/lymphatics/nevers

Outer Layers:

• On Liver side = adventia – (CT layer rich in elastic fibers, n fibers, adipose tissue – no peritoneal coverage)
  • if is adventia, will have intercalated ducts to absorb bile and aberrant bile ducts = Ducts of Luschka
    • these ducts are non-functional
    • located on post wall of GB
    • may be present, are remnants of bile duct system
    • look like small lumen surrounded by cuboidal epithelium
    • none are connected to lumen of GB, some may be connected to liver
• On unattached side = serosa – (visceral peritoneum, layer of mesothelium and loose CT
  • subserosa with it = thin squamous like layer

Embryology of Liver/Gallbladder

• Liver primordium appears in the middle of 3. week, as outgrowth of the endodermal epithelium at the distal end of the foregut
• This outgrowth, the hepatic diverticulum, or liver bud, consits of rapidly proliferating cells that penetrate the septum transversum= the mesodermal plate between the pericardial cavity and the stalk of the yolk sac.
• While hepatic cells continue to penetrate the septum, the connection between the hepatic diverticulum+ the forgut (duodeneum) narrows, forming the bile duct.
  
• A small  ventral outgrowth is formed by the bile duct, + and this outgrowth gives rise to the gallbladder+ the cystic duct.
• During furhter development, epithelial liver cords intermingle with the vitelline + umbilical veins, which form hepatic sinusoids.
• Liver cords differentiate into the parenchyme(liver cells) + form the lining of the biliary ducts.
• Hematopoietic cells, Kupfer cells + CT cells are derived from mesoderm of the septum transversum
• When liver cells have invaded the entire septum transversum, so that the organ bulges caudally into the abdominal cavity–> mesoderm of the septum transversum lying between the liver and the foregut+ the liver+ ventral abdominal wall become membranous –> forming the lesser omentum+ falciform ligament.
• Together, having formed the peritoneal connection between the forgut+ the ventral abdominal wall, they are known as the ventral mesogarstrium.

The surface of the liver differentiate into visceral peritoneum, exept on its cranial surface.

• In this region, the liver remains in contact with the rest of the original septum transversum.
• this portion of the septum, which consits of densey packed mesoderm, will form the central tendon of the diaphragm
• the surface of the liver that is in contact with the tendon of the diaphragm = bare area of the liver (never covered by peritoneum)
  

@ 10 th week: weight of liver app. 10 % of the total body weight

• this may be attributed partly to the large numbers of sinusoids,also imp. Factor: is its hematopoietic function.
• large nests of proliferating cells, which produce red + white blood cells, lie between hepatic cells+ and wall of the vessels.
• this activity gradually subsides, during the last 2 month of intrauterine life + only small hematopoietic islands remain at birth.the weight of the liver is then only 5% of the total body weight.

@ 12th week: bile is formed by hepatic cells

• since the gallbladder + cystic duct have developed + the cystic duct has joined the hepatic duct to form the bile duct, bile can enter the gastrointestinal tract, consequence= contents take on a dark green colour.
• due to positional changes of the duodenum, the entrance of the bile ducts gradually shifts from the initial ant. position to a posterior one, and consequently the bile duct passes behind the duodenum.

18. The peritoneum. The peritoneal cavity. The development of the peritoneum.. The histology of tonsils.

Anatomy of the peritoneum & the peritoneal cavity.

• Definition of Peritoneum = is  a continuous, glistening+ slippery transparent serous membrane,  lines the andominopelvic cavity+ invests the viscera.

• The peritoneum consists of two continuous layers, both layers of peritoneum consists of mesothelium, a layer of simple squamous epithelial cells:
  • Parietal peritoneum, which lines the internal surface of the abdomino-pelvic wall
    • has same a/v/n/lymphatics, as the region of wall that it covers
    • is sensitive to pressure, pain, heat+ cold+ laceration.
    • Remember = Parietal = Pain* same goes for parietal pleura in thoracic cavity
    • Pain from FOREGUT = expressed in EPIGASTRIC region, MIDGUT = UMBILICAL region, HINDGUT = PUBIC region.
    • nerve supply = phrenic n, lower IC n, subcostal n, Iliohypogastric n, Ilioinguinal n
  • Visceral peritoneum, which covers visceral organs like the stomach+ intestines.
    • has same a/v/n/lymphatics, as the organ it covers
    • Stimulated primarily by stretching + chemical irritation
    • nerve supply = visceral n, ANS pathways

RELATIONSHIP of the VISCERA TO THE PERITONEUM:

• Intraperitoneal organs:  are almost covered with visceral peritoneum (e.g. the stomach+ spleen)
• Extraperitoneal – only organ that is extra– peritoneal is the ovary
• Retroperitoneal – 2 types – more on this later
  • Primary  – always has been located behind the peritoneum
  • Secondary – was originally intraperitoneal, but now is located behind the peritoneal cavity
• Infraperitoneal – located below the peritoneal cavity, usually covered superiorly with peritoneum

PERITONEAL REFLECTIONS – support viscera and contain a/v/n

1 Sup point of peritoneum, 2 inner aspect of the abdominal wall , 3 superior surface of the urinary bladder, 4 over the uterus in the female, 5 into the pouch of Douglas, 6 anterior surface of the rectum onto the posterior abdominal wall, 7 root of the mesentery of the small intestine. 8 horizontal part of the duodenum, 9 gastrocolic ligament, GO= greater omentum (11), 12 anterior surface of the stomach, 13 lesser omentum, EF = epiploic foramen, LPC = lesser peritoneal cavity (lesser sac)

Omentum

• Lesser Omentum – double layer peritoneum, from porta hepatis –> lesser curve + sup hor part of duodenum
  • hepatogastric & hepatoduodenal ligaments
  • form ant wall of lesser sac
  • carry L & R gastric a/v b/w 2 layers of peritoneum
  • free lower margin for = proper hepatic a, bile duct, and portal v
• Greater Omentum – hangs down like apron from gr. curve of stomach –> covering transverse colon & other ab viscera
  • carry R & L gastroepiploic a/v along greater curve
  • adheres to areas of inflammation and wraps around inflammed areas
  • prevents serous diffuse peritonitis = accumulating peritoneal fluid w/ fibrin & leukocytes

Mesentaries

• Mesentary Proper – fan shaped double fold of peritoneum, suspends jejunum & ileum from post ab wall
  • forms a root (duod-jej flexure –> R iliac fossa)
  • free border encloses SI
  • contains sup mesenteric & SI a/v/n/lymph vessels
• Transverse Mesocolon – connect post surfac of transv. colon –> post ab wall
  • fuses w/ gr. omentum to form gastrocolic lig
  • contains middle colic a/v/n/lymphatics
• Sigmoid Mesocolon – inverted V shaped peritoneal fold
  • connects sigmoid colong to pelvic wall
  • contains sigmoid a/v
• Mesoappendix – connects appendix to mesentery of ileum
  • contains  appendicular a/v

Peritoneal Folds –  reflections w/ free edges

• Umbilical folds – 5 folds of peritoneum below umbilicus
  • Lat umbilical folds = contain inf epigastric a/v
  • Medial umbilical folds = contain umbilical a
  • Median umbilical folds = contain remnant of urachus = connects urinary bladder of the fetus with the allantois, a structure that contributes to the formation of the umbilical cord
• Retrouterine folds – extension from cervix of uterus, along side of rectum to pelvic wall (post) and form Rectouterine pouch of Douglas
• Ileocecal fold – terminal ileum –> cecum

Peritoneal Ligaments

• Gastrosplenic lig – from L greater curve –> hilus of spleen, has short gastric a/v, L gastroepiploic a/v
• Splenorenal lig – Hilus of spleen –> L Kidney, has splenic a/v, has tail of pancreas
• Gastrophrenic lig – Upper greater curve –> diaphragm
• Gastrocolic lig – Greater curve –> transverse colon, absorbed into greater omentum, usually
• Phrenicocolic lig – Colic flexure –> diaphragm
• Falciform lig – sickle shaped peritoneal fold, connects liver –> diaphragm & ant ab wall
  • border b/w R & L Lobe (ant)
  • contains ligamentum teres hepatis, and paraumbilical v, which cxts L portal v w/ subcut v in umbilical regions
• Ligamentum Teres Hepatis – aka round ligament of liver, lies in lower free marginof falciform ligament, is L border of quadrate lobe on visceral surface of liver, remnant of umbilical v
• Coronary Lig – peritoneal reflection from diaphragmatic surface of liver  onto diaphragm, encloses bare area of liver
  • has R & L extensions that form R & L triangular ligaments
• Ligamentum Venosum – fibrous remnant of ductus venosus, lies in fissure  on inf surface of liver, forms L border of caudate lobon visceral surface of liver 

 

Start @ 1 and follow around the peritoneal cavity. 2. Back of the abdomen, anterior surface of the right kidney, pass through the epiploic foramen, along the posterior wall of the lesser peritoneal cavity, 3 then up along the renal lienal ligament 4 onto the posterior surface of the stomach 5. Your finger will continue through the epiploic foramen again to turn around the free margin of the lesser omentum 6, then over the anterior surface of the stomach again 7. Continue to follow around the greater curvature of the stomach 8 until you reflect again along the gastrolienal ligament 9. Your finger will now pass around the spleen, onto the left kidney to the parietal peritoneum and back to the falciform ligament fl.

THE PERITONEAL CAVITY

• located within the abdominal cavity &  continous inf. to the pelvic cavity.
• =  a potenial space between the parietal+ visceral layers of peritoneum
• contain no organs
• contains a thin film of peritoneal fliud = which is composed of water, electrolytes+ other substances derived from interstitial fliud in adjacent tissues.
• peritoneal fluid lubricates the peritoneal surfaces, enabling the viscera to move over each other without friction and allowing the movements of digestion
• Contains leukocytes+ antibodies that resists infection.
• Lymphatic vessels, particularly on the inf.surface of the unceasingly active diaphragm, absorb the peritoneal fluid.

In  Males: the peritoneal cavity is completely closed

In Females: connected to extra-peritoneal cavity through the uterine tubes, uterine cavity, & vagina

• split into Lesser Sac & Greater Sac

Lesser Sac = Omental Bursa

• irregular space that lies behind liver, lesser omentum, stomach, upper ant part of greater omentum
• closed sac, except for cxn w/  greater sac via epiploic foramen
• 3 recesses:
  • Sup. recess – being liver, stomach, lesser omentum
  • Inf recess – behind stomach, extends into layers of greater omentum
  • Splenic recess – extends to the L to the hilus of spleen

Greater Sac

• extends across entire area of abdomen and from diaphragm –> pelvic floor
• 5 recesses:
  • Subphrenic recess – peritoneal pocket b/w diaphram & ant/sup part of liver
    • separates into R & L recesses by falciform lig
  • Subhepatic recess – peritoneal pocket b/w liver & transverse colon
  • Hepatorenal recess – deep peritoneal pocket b/w liver (ant) & kidney (post)
  • Morison’s pouch = formed by R subhepatic & hepatorenal recess
    • comminucates w/ subphrenic recess, lesser sac via epoploic foramen, and R paracolic gutter(to pelvic cavity)
  • Paracolic recess – (aka gutters) – lies lat to asc/desc colon

Epiploic foramen (of Winslow) – natural opening b/w lesser and greater sacs

• Sup = peritoneum of caudate lobe of liver
• Inf = peritoneum of 1st part of duodenum
• Ant = free edge of lesser omentum
• Post = peritoneum covering IVC

Retroperitoneal Space

The retro peritoneal space is seperated into the 3 compartments by the renal fasica. This fascial covering is like a tent that is closed susuperiorly and open inferiorly.

Ant Chamber = b/w peritoneum and renal fascia, has all secondary retroperitoneal organs

• asc colon
• desc colon
• duodenum (except sup hor part)
• pancreas (except tail, sometimes)
• Br. of sup mesenteric a, celiac trunk, sup/inf mesenteric v, portal v, common bile duct

Middle Chamber = w/in renal fasica, has primary retroperitoneal organs.

• kidneys
• suprarenal glands
• ureters
• Ab aorta + branches
• IVC + branches
• Thoracic duct
• Cisterna Chyli

Post Chamber = b/w renal fascia and transverse fascia(post ab wall)

• asc lumbar v (becomes azygos v, once crosses diaphragm into thoracic cavity)
• Greater/Lesser splanchnic n
• SNS trunk
• Subcostal n.
• Lumbar plexus + branches
• Ilioinguinal n.
• Inohypogastric n
• Obturator n
• Genitofemoral n
• Gonadal a/v

Histology – Tonsils

Slide #25 Palatine Tonsils *H&E

 Structures to Identify:

• tonsillar crypts
• str. sq. non keratinizing epith
• lymph nodules (primary and secondary)
• muscle bundles
• germinal centers
• CT capsule 

With naked eye: dark, blue, partially encapsulated specimen w/ deep crypts

General Info:

• The palatine tonsilles(faucial tonsils)are paired, ovoid structures that consits of dense accumulation of lymphatic tissue located in the mucous membrane of the fauces(the junction of the oropharynx + oral cavity).
• The epithelium that forms the surface of the tonsil dips into the underlying CT in numerous places, forming crypts known as tonsillar crypts.
• Numerous lymphatic nodules are evident in the walls of the crypts.
• Tonsils guard the opening of the pharynx, the common entry to the respiratory+ digestive tracts.
• CLINCAL NOTE: can become inflamed because of repeated infection in the oropharynx+ nasopharynx+ can even harbour,
  • bacteria can cause repeated infections if they are overwhelmed.
  • debris and abcteria that collects in tonsilar crypts are hard to clean, as not enough saliva to clean them
  • When this occurs, the inflamed palatine tonsils+ pharyngeal tonsils ( also called adenoids) are removed surgically.

Important Histological Features

• C.T. capsule on one side, oral mucosa on other side

• Stratified squamous nonkeratinizing epithelium, lymphocytes invade epithelium within the crypt

  • this epith is present in both palatine and lingual tonsils

• Mucous membrane, lamina propria enlarged contains lymphatic nodules

  • NOTE = W/in nodule s= B lymphocytes, b/w them = T lymphocytes 

• Stroma, each lobules has a cortex+ medulla, the cutting plane of the section determines whether you can see both or not

• surrounded by a  dense fibroelastic CT capsule (red)

• Extends trabeculae to the margin of the cortex and medulla, which can contain fat, a/v

• Below CT capsule = skeletal m fibers,  but not as much as in lingual tonsil

• CORTEX- darker stained(blue)

  • Blood vessels with epithelioreticular cell sheath, cytoreticulum

  • Different than CT has no reticular fibers

  • Contains epithelioreticular cells as the stroma. Ovoid nucleus, larger cell, lighter colour = lymphoreticular mesrk

• large # of High Endothelial Venules (HEVs)

Embryo

• Develops form endoderm instead of mesoderm, unlike regular ct, mostly small lymphocytes
• epithelial lining of 2nd pharyngeal pouch – forms buds that penetrate surrounding mesenchyme
• mesenchyme => becomes palatine tonsil primordium
• in 3rd – 5th, invaginated by lymph tissue, forming tonsil

Slide #26 Lingual Tonsils *H&E

Structures to Identify:

• tonsilar crypts
• CT
• salivary glands
• Str. Sq. non-keratinizing epith
• lymph nodules
• skeletal m

With Nake Eye: A solid specimen with a darker region on one side

General Info:

• aggregation of lymph tissue located at root of tongue, posterior to sulcus terminalis
• not usually inflammed, as very accessible to saliva, and tonsilar crypts are not that deep for debris to collec

Histological Characteristics:

• has a str. squamous non-keratinized epith – very characteristic of oral mucosa, lines surface, and dips down in very shallow tonsillar crypts
• tonsillar crypts form deep invaginations on surface of tongue, ext. deep into LP
• Many lymph nodules, some secondary.
  • nodules =  B lymphocytes, b/w nodules = T lymphocytes
• LP = adipose tissue,  mucus acini of lingual glands, ducts of glands, lymphoreticular tissue
• Below LP, is the skeletal musc. coming from the tongue – bright red color

To be sure it is lingual tonsil = look for the str sq non kerat epith, large amts of skeletal m, lingual mucus glands, NO CT capsule

Embryology – The development of the peritoneum

The peritoneum develops ultimately from the mesoderm of the trilaminar embryo. As the mesoderm differentiates, one region known as the lateral plate mesoderm splits to form two layers separated by an intraembryonic coelom. These two layers develop later into the visceral and parietal layers found in all serous cavities, including the peritoneum.

As an embryo develops, the various abdominal organs grow into the abdominal cavity from structures in the abdominal wall. In this process they become enveloped in a layer of peritoneum. The growing organs “take their blood vessels with them” from the abdominal wall, and these blood vessels become covered by peritoneum, forming a mesentery