27. The portal vein. The portal-systemic anastomoses. The lymphatic dranaige of the abdominal and pelvic organs. The histology of the suprarenal gland. Development of the 2 external features of the fetus. External features of a matured newborn. Twin pregnancy. Fetal membranes in twins.

27. The portal vein. The portal-systemic anastomoses. The lymphatic dranaige of the abdominal and pelvic organs. The histology of the suprarenal gland. Development of the 2 external features of the fetus. External features of a matured newborn. Twin pregnancy. Fetal membranes in twins.

Anatomy: The portal vein. The portal-systemic anastomoses. The lymphatic dranaige of the abdominal and pelvic organs.

Portal Venous System

system of vessels in which blood collected from structures of the primitive gut – all unpaired visceral organs.
Ex/
Stomach, Spleen, Liver, Intestines, Pancreas, GB

From those organs –> portal v –> liver sinusoids –> IVC (after filtration)

Portal v – formed by union of splenic v & sup mesenteric v, just post to border b/w head and neck of pancreas
Inf mesenteric v joins either one or jxn b/ w the two
located in Porta Hepatis b/w hepatic a proper, common bile duct
w/in hepatoduodenal ligament

Carries into Liver:

• hormones – Insulin, Glucagon, Somatostatin from pancreas
• RBC degradation products (ex/ bilirubin)
• Absorbed food + other materials (not lipids) – amino acids, H20, salts, sugars etc
• antibodies secreted by spleen products

Veins that drain into portal v

1. Sup mesenteric v –
   • w/ a @ R side of mesenteric root,
     
   • rec veins that correspond to art of sup mesenteric a
   • Inf pancreaticoduodenal v, L colic v, middle colic v
2. Splenic v – union of branches from around spleen
   • Short gastric v, splenic br, pancreatic br, L gastroepiploic v
3. Inf mesenteric v – union of sup rectal v, sigmoid v, L colic v
4. L gastric v
5. Paraumbilical v – in falciform lig, usually closed
   • but dilate in portal hypertension
   • connect  L branches of portal v w/ sub cutaneous v in umbilical region
   • (br of sup/inf epigastric, thoracoepigatric + sup epigastric v)

Portal Systemic Anastomosis
B/w portal system & either SVC/IVC
very important, since need to fxn during liver insufficiency,
to transport blood from portal –> systemic circulation directly
CLINICAL NOTE:   Portal Hypertension – Inc BP in portal v system, caused by pregnancy, cirrhosis of liver –> blood will flow to lower pressure areas –> veins that are anastomosed w/ veins that will flow into vena cava instead

1. Esophageal Anastomosis

• formed b/w L gastric (to portal v) of stomach + esophageal v (azygos system)
• In case of portal hypertension, these veins can enlarge or erupt –> bleeding
• esophageal v located w/in walls of esophagus,
• if they enlarge – will protrude more into lumen of esophagus
• if erupt can cause bleeding into lumen of esophagus = verices

2. Rectal Anastomosis

• b/w sup rectal v (inf mesenteric v) + mid rectal v (int iliac v) = hemorroidal v
• In case of portal hypertension,  veins of int hemorrhoidal plexus enlarge & cause  internal hemorrhoids

3. Paraumbilical Anastomosis

• located around umbilicus
• b/w sup/inf epigastric & paraumbilical v
  • Inflow limb is recanalized umbilical v (in round lig of liver)
  • Outflow limb is towards the superficial + deep abdominal anastomosis systems
  • Special v located around umbilicus
  • running radial towards it, establish the connection b/w inflow – outflow part = paraumbilical v
• In portal hypertension, paraumbilical v. enlarges, elevate from ant ab wall, causing classical symptom = Caput medusae

4. Retroperitoneal anastomosis

• loc @ retropertineum, least important connection
• formed b/w v of abdominal v & v of duod/colon = veins of Retzius
• these veins could be cut if enlarges – bleeding in retroperitoneal space

The lymphatic drainage of the abdominal and pelvic organs.

Histology:The histology of the suprarenal gland.

Embryology: Development of the 2 external features of the fetus. External features of a matured newborn. Twin pregnancy. Fetal membranes in twins.

9th week –> birth = fetal period
growth in length = 3/4/5th months –>
CRL = crown-rump length
CHL = crown-heel length

Month 4 (see figure)

External Features: At four months fetal skin is transparent enough for underlying blood vessels to be seen clearly. Fingernails are well established and toenails begin to form. Nostrils by this time are almost formed and eyes move from the lateral sides of the head to the ventral side. Soft and thin hairs, called lunugo hairs, begin to grow on the scalp

Month 5

External Features: At five months, sebaceous glands accumulated at the surface of the skin begin to deposit verniz caseosa, which serves as a protective coating for the epidermis. The lanugo hairs that began formation during the fourth month now cover most of the entire body. Eyelids and eyebrows develop and abdomen begins to fill out.

Month 6

External Features: By the sixth month and the end of the second trimester, fetal skin is now red and wrinkled and lanugo hairs have darkened.

Month 7

External Features: At seven months, the fetus continues the development of hair and the scalp hairs grow beyond the length of the thin lanugo hairs that developed during the second trimester. Eyelashes are well developed and eyelids begin to open.

Month 8

External Features: By the eighth month, the skin is pink and smooth, the eyes are capable of reacting to light and the fingernails have grown long enough to reach the tip of the fingers.

Month 9

External Features: Toenails grow up to the tip of the toes and fingernails grow beyond the fingertips. The skin is fully covered in vernix caseosa (which serves to protect the epidermis) and most of the lanugo hairs are shed. By this time, the placenta weighs about 500grams and the umbilical cord becomes central in the abdomen.