Tag Archives: retroperitoneal

36. The anatomy, histology and development of the ureter, urinary vesicle and urethra.

6 Jan

36. The anatomy, histology and development of the ureter, urinary vesicle and urethra.

Anatomy of the ureter, urinary vesicle and urethra.

Ureter

*retroperitoneal
General Info:
musc tube that transmit urine via peristaltic waves, leads from kidney

is the most posterior structure that emerges from hilus of kidney
25-30 cm long
enter bladder @ anteromedially, superior to levator ani

Topography:

  • crosses bifurcation of common iliac a @ pelvic brim
  • desc retroperitoneally on lat pelvic wall –> med to umbilical a & obturator a/v
  • post to ovary @ post surface of ovarian fossa
  • 1-2 cm lat to uterus, runs w/ uterine a, which runs above and ant to base of broad lig
  • passes post/inf to ductus deferens & lies in front of seminal vesicle before entering post/lat bladder (male)


2 parts – abdominal/pelvis


Abdominal

crossed by 3 structures: Topography
1. Gonadal a/v – in front
2. Psoas major – behind
3. Bifurcation of common iliac a w/ ureter in front of int iliac a

Male – ductus deferens crosses ureter in front

Female

  • uterine a crosses in front
  • @ bifurcation of common iliac, forms post border of ovarian fossa
  • contacts lat fornix of vagina b4 entering bladder

Blood Supply:

  • rec blood from aorta, renal, gonadal, common & int iliac, umbilical, sup/inf vesicle a, middle rectal a
  • Vesicle venous plexus –> int iliac v (sometimes, prostatic vesicle plexus)

Lymph Drainage: lumbar, common iliac, ext iliac, int iliac l.n

Urinary Bladder


*Infraperitoneal – lower in female
located in pelvis minor when empty
located full, can enter major pelvis –> even up to umbilicus

General Info:

  • THICK muscular wall = detrusor m
  • holds urine, until ready to release it
  • mucus membrane attaches, except @ trigone
    • mucus membrane attaches to CT underlying, no mucosal folds
    • originates from mesonephric duct
    • marked by entrances of ureter & ejaculatory duct
    • has 2 ureteric openings and urethral openings (int urethral sphincter)
  • anchored by CT ligaments = paracysticum
  • held @ neck  to pubic bone, via puboprostatic (male), or pubovesical (female) ligaments

Structure of Bladder (Detail):

The bladder itself consists of 4 layers:-

(1) Serous – this outer layer being a partial layer derived from the peritoneum,
(2) Muscular – the detrusor muscle of the urinary bladder wall, which consists of 3 layers incl. both longitudinal and circularly arranged muscle fibres,
(3) Sub-mucous a thin layer of areolar tissue loosely connecting the muscular layer with the mucous layer
(4) Mucous – the innermost layer of the wall of the urinary bladder loosely attached to the (strong and substantial) muscular layer. The mucosa falls into many folds known as rugae when the bladder is empty or near empty.

  • The features observable on the inside of the bladder are the ureter orifices, the trigone, and the internal orifice of the urethra.
  • The trigone is a smooth triangular region between the openings of the two ureters and the urethra and never presents any rugae even when the bladder is empty – because this area is more tightly bound to its outer layer of bladder tissue.

Peritoneal relations of bladder:

Outer surfaces of the Bladder: The upper and side surfaces of the bladder are covered by peritoneum (also called “serosa”). This serous membrane of the abdominal cavity consists of mesthelium and elastic fibrous connective tissue. “Visceral peritoneum” covers the bladder and other abdominal organs, while “parietal peritoneum” lines the abdomen walls.

Topography of Bladder: Bladder Bed

  • ant = pubic bone, separated from ant ab wall & pelvis by rectopubic space
  • inf/lat = obturator int m, levator ani m
  • inf/post = rectum

B/w bladder & rectum:
Male – seminal vesicles & ejaculatory duct, ductus deferens
Female – uterus & upper vagina

female-sagittal-section

Vesicouterine Pouch:
ant = bladder
post = uterus
lat = vesicouterine ligaments (folds)

Normally, pouch so small, there is nothing in it
If Rectoversion occurs, may contain SI loops
bladder connected to CT except @ neck where puboprostatic lig anchors it (male)

Rectovesicle Pouch:
ant = bladder, seminal vesicle, DD
post = rectum
lat = rectovesicular fold

In male, pertioneum covers fundus, reflecting from upper post wall, and covers tip of seminal vesicle

male-sagittal-section

Parts of Bladder:

  1. Apex (ant end)
    • retro to symphysis
    • origin of median umbilical ligament – remnant of embryonic urachus (connection b/w urinary bladder and embryonic allantois)
  2. Fundus (post/inf)
    • contact w/ rectum in male, separated by rectovesicular septum
    • contacts w/ ant surface of vagina in female
  3. Neck (lat/post — converges here)
    • urethra originates from bladder here
    • just above = uvula – small eminence projects into urethra

Blood Supply:

  • Sup vesicle a (int iliac a)
  • Fundus of bladder
    • inf vesicle a (Male)
    • vaginal a (uterine a – Female)
  • veins = vesicle venous plexus –> int iliac v (prostatic venous plexus)

Lymph Drainage:

  • body = ext iliac lymph nodes
  • fundus = int iliac l.n
  • neck = sacral & common iliac l.n.

Innervation:

  • PNS from pelvic splanchnic n (S2-4)
    • VM for detrusor m
    • (-) for int urethral sphincter
  • SNS (T12-L2)
    • VM for int urethral sphincter
    • (-) detrusor m

Urethra
From bladder –> opens @ perineum, urine emptied thru it

Male Urethra


Parts to it:
1. Prostatic urethra
3 cm long, and w/in prostate
widest part of urethra
covered w/ urothelium = transitional epithelium

The prostatic urethra begins at the neck of the bladder and includes all of the section that passes through the prostrate gland. It is the widest and most dilatable part of the male urethral canal.

Structures opening here:
1. Prostatic glands
2. Ejaculatory ducts
3. Prostatic utricle

long ridge = urethral crest

  • runs through out w/ 2 grooves beside it = prostatic sinuses
  • opening of submucosal ducts & prostatic glands
  • @ upper crest = seminal collicus

Seminal colliculus

  • small hill like structures protruding into urethra
  • lat to colliculus are prostatic sinuses, where prostate glands open
  • 3 small openings:
    • @ midline = utricle of prostate (remnant of paramesonephric duct – regresses in male)
    • inf to that = 2 ejaculatory ducts

secretions of prostate, seminal vesicle, and bulbourethral glands mixes w/ spermatozoa from testis = semen

2. Membranous urethra
1 cm long
passes thru UG diaphragm – here ext urethral sphincter seen

The membranous urethra is the shortest and narrowest part of the male urethra. This section measures approx. 0.5 – 0.75 inches (12 – 19 mm) in length and is the section of the urethra that passes through the male urogenital diaphragm.
The external urethral sphincter (muscle) is located in the urogenital diaphragm (as for the female urethra).
The passage of urine along the urethra through the urogenital diaphragm is controlled by the external urethral sphincter, which is a circular muscle under voluntary control (that is, it is innervated by the somatic nervous system, SNS).

3. Penile urethra
enters bulbous part of  penis
Pathway: turns up @ sharp angle (1st turn)  –> runs along bulb of penis –> to pubic symphysis –> bends down (2nd turn) –> corpus spongiosum –> runs down to tip of penis & opens @ navicular fossa

The spongy (penile) urethra is the longest of the three sections. It is approx. 6 inches (150 mm) in length and is contained in the corpus spongiosum that extends from the end of the membranous portion, passes through the penis, and terminates at the external orifice of the urethra – which is the point at which the urine leaves the body.

@ navicular fossa: str columnar –> str sq non keratinazing epith

CLINICAL NOTE: B/c of 2 sharp bends – makes it difficult to insert catheter

Blood supply: prostatic br of inf vesicle a & middle rectal a, v follow a

Lymph Drainage: int/ext iliac l.n

Nerve supply: pudendal n, prostatic plexus (inf hypogastric plexus)

male-urethra

Female urethra

female-urethra

At only about 1.5 inches (35 mm) long, the female adult urethra is shorter than the adult male urethra (approx. or 8 inches, or 200mm). The female urethra is located immediately behind (posterior to) the pubic symphysis and is embedded into the front wall of the vagina.

The urethra itself is a narrow membranous canal that consists of three layers:

  1. Muscular layer – continuous with the muscular layer of the bladder, this extends the full length of the urethra.
  2. Thin layer of spongy erectile tissue – including plexus of veins and bundles of smooth muscle fibres. Located immediately below the mucous layer.
  3. Mucous layer – internally continuous with the bladder and lined with laminated epithelium that is transitional near to the bladder.

After passing through the urogenital diaphragm (as shown in the diagram), the female urethra ends at the external orifice of urethra – which is the point at which the urine leaves the body. This is located between the clitoris and the vaginal opening.

The passage of urine along the urethra through the urogenital diaphragm is controlled by the external urethral sphincter, which is a circular muscle under voluntary control (that is, it is innervated by the somatic nervous system, SNS).

The female urethra is a much simpler structure than the male urethra because it carries only urine (whereas the male urethra also serves as a duct for the ejaculation of semen – as part of its reproductive function
upper 1/2 = prostatic urethra
lower 1/2 = “membranous”

@ upper part = Paraurethral glands –> ducts @ ext urethral orifice

@ lower part
goes through UG diaphragm
transverse perineal m wraps around to form = urethro vaginal sphincter
closely associated w/ ant wall of vagina

  • attached via strong CT sheath = urethrovaginal septum
  • b/w them = urethrovaginal space

Blood supply: int pudendal a, vaginal a, veins follow a

Lymph Drainage: sacral/int iliac l.n

Nerve supply: pudendal n


Process of Urination:
Initiated by (+) of stretch receptors in detrusor m in bladder in wall by inc volume of uring
innervated by S2-4 via pelvic splanchnic n
can be assisted by contraction of abdominal m = inc intra abdominal & pelvic pressures

Process:
1. SNS = (+) relaxation of bladder wall
contract inner sphincter –> (-) emptying
may stimulate detrusor m to prevent reflux of semen into bladder during ejaculation

2. PNS = preggl fibers in pelvis splanchnic n
synapse in pelvic (inf hypogastric plexus)
post ggl to bladder musc induc reflex = contraction of detrusor m
and relaxation of int sphincter
inc urge to urinate

3. SM fibers in pudendal n cause voluntary relaxation of ext urethral sphincter
bladder begins to release

4. @ end of urination
the ext urethral sphincter ( & bulbospongiosus m in male) contracts
expel the last few drops of urine from urethra

Histology  of the ureter, urinary vesicle and urethra.

Slide #63 Ureter * H&E


Structures to Identify:

  • 3 layers = mucosa, muscularis, adventia
  • transitional epith
  • umbrella cells
  • a/v
  • CT
  • piriform cells
  • basal cells

General Info

  • paired tubular structures that convey urine from kidney –> bladder
  • lined w/ transitional epith to adapt to changing environment (fluid v no fluid)

Mucosa

  • Epith = urothelium
    • thick, with cells that change shape
  • star shaped irregular lumen, made by mucosal folds, due to musc. contractions
  • Note that lumen is long , narrow and star shaped, not circular *like DD
  • 3 main cell types of Epith
    • umbrella cells – come in contact with urine, and adjust accordingly, can be bi-nucleated, shape change due to actin filaments
    • piriform cells – underneath umbrella cells and above basal cells, can also adjust morphologically
    • basal cells – located at lowest layer of stratified epith
  • LP = fibroelastic CT, denser near epith –> looser towards muscularis ext, with diffuse lymph tissue = MALT
  • No real muscularis mucosae
transitional epithelium or urothelium and cells of it

transitional epithelium or urothelium and cells of it

Muscularis Ext

  • 3 layers:
    • inner longitudinal layer
    • middle circular layer
    • outer longitudinal – but only in last 1/3 of ureter
  • smooth m responsible for creating peristaltic contractions to convey urine through ureter (30cm)

Adventia

  • 3rd main layer
  • ureter = retroperitoneal, so covered w/ adventia
  • CT + a/v/n
  • adipose

Slide #64 Urinary Bladder * H&E

Contracted Bladder - Our slide doesnt look like this, but this shows layers well

Structures to Identify:

  • urothelium
  • muscularis
  • a/v
  • CT
  • mesothelium
  • PNS ggl

General Info

  • Receives urine from 2 ureters and under appropriate stimulation, will secrete it through urethra
  • lined by urothelium, which allows bladder to adjust to amount of urine

Mucosa

  • Epith = urothelium,  transitional epithelium
    • same cell types as ureter
    • up to 10 layers when bladder empty, # layers dec when bladder is full
  • when bladder is full, cells flatten and appear squamous, & when bladder was empty, cells became dome shaped
  • LP = CT tissue fibers, fibroblasts, a/v, many layers
    • Can either say LP has 2 layers = upper cell rich, and lower fibrous layer
    • Or can say there is a cell rich LP with a fibrous submucosa
    • fibrous layer not present in bladder trigone
  • changes in appearence and cells shapes in transitional epithelium are from thickened regions called plaques
    • interconnected via interplaque regions
    • allow  cell membrane to fold – which disappear when urine flows into bladder

Muscularis Mucosae

  • 3 muscular layers: – inner longitudinal, middle circular, outer longitudinal
  • not as organized as ureter
  • may be ggl cells wich are part of ANS
    • helps regulate urine secretion via relaxation & contraction of muscularis
    • controls detrusor m
  • Internal urethral sphincter = fromed @ site of entry of bladder –> Urethra
  • w/ CT in between, and a/v and capillaries, and occasional n. fibers

Adventia

  • Infraperitoneal
  • fundus covered by peritoneum
  • serosa/ subserosa can be present where peritoneal pres – superiorly –> simple squamous = mesothelial cells
  • SNS n fibers maybe

Beyond the serosa/adventitia covering of the bladder is perivesical fat.  This is a layer of fat surrounding bladder.

Its upside down - sorry

It's upside down - sorry

Slide #71 Penile Urethra * H&E

Structures to Identify:

  • lumen
  • corpus spongiosum
  • smooth m
  • str columnar/ psuedo str columnar
  • tunica albuginea
  • urethral glands of Littre
  • paraurethral ducts
  • endo-epith glands

Mucosa

  • Epith = pseudostratified non keratinized epith
    • epith changes depend on part of urethra
    • Pars prostatica –  urothelium
    • Pars membranous – str columnar
    • Pars spongiosum –  str columnar – until navicular fossa – str squamous
  • LP = thin layer, merges with surrounding corpus spongiosum, cell rich
  • lumen is shaped like ureter, but does NOT have urothelium in our slide, so look for that, and the glands of Littre
  • mucosal folds makes small dips in lumen, and forms lacunae
  • lacunae attached to urethral ducts of urethral glands of Littre
    • mucus secretions
    • thin basophillic (blue) outer layer with pale interior (mucus)
    • duct is more basophillic, with small circular lumen

Corpus spongiosum

  • network  of cavities lined by simple squamous epith
  • a/v in b/w

Outer layer = Tunica albuginea

  • thick eosinophillic layer, with smooth m and elastic fibers
Ducts of Littre

Ducts of Littre

Development of the ureter, urinary vesicle and urethra.

Ureter:

  • intermediate mesoderm forms longitudinal ridge on post body wall = urogenital ridge
  • part of UG ridge becomes nephrogenic cord –> urinary system
  • nephrogenic cord develops into 3 structures: pronephros, mesonephros, metanephros
  • metanephros further develops from ureteric bud and from grouping of mesoderm w/in nephrogenic cord, metanephric mesoderm
  • further development of ureteric bud –> becomes ureters

Urinary bladder:

  • urinary bladder is formed from upper end of urogenital sinus, continuous w/ allantois
  • allantois becomes fibrous cord = urachus * stays in adult as median umbilical lig
  • lower end of mesonephric ducts –> post wall of bladder as trigone
  • mesonephric ducts open into urogenital sinus below bladder
  • transitional epith from endoderm

Urethra:

Female Urethra:

  • female urethra is formed from lower end of urogenital sinus
  • develops as endodermal outgrowths into surrounding mesoderm = urethral glands, paraurethral glands
  • end @ vestibule of vagina, also forms from urogenital sinus
  • vestibule of vagina – develop endoderm growths = greater vestibular glands
  • endoderm = epith

Male Urethra:

  • Prostatic urethra, membranous urethra, prox urethra
    • formed from lower end of urogenital sinus
    • endoderm = transitional epith, str columnar epith
    • prostatic urethra have endoderm outgrowth into mesoderm = prostate gland
    • membranous urethra have endoderm outgrowth into mesodem = bulbourethral glands
    • prox part of penile urethra have endoderm outgrowth into mesoderm = Littre’s glands
  • distal part of penile urethra
    • formed from ingrowth of surface ectoderm = glandular plate
    • glandular plate joins penile urethra and becomes tube = navicular fossa
    • ectodermal septa lat to navicular fossa –> becomes foreskin
    • str sq epith lines part of urethra = ectoderm
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18. The peritoneum. The peritoneal cavity. The development of the peritoneum.. The histology of tonsils.

18 Dec

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.

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

 tns02he1Structures 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