Digestive system Flashcards
peritoneal relationship of LI
ascending colon, descending colon and rectum are retroperitoneal
appendix, transverse colon, sigmoid colon are intraperitoneal
caecum is variable
distinguishing features of the large intestine
semilunar plicae –> internal mucosal folds that are not complete circular.
haustra –> one haustrum is bordered by two neighbouring semilunar plicae, because tania are shorter than the length of the large intestine giving rise to sacculations
tenia coli –> 3 band like structures compose of segregated outer longitudinal muscular layer
epiploic appendages –> fat filled peritoneum projecting from right and left borders of the free tania. are more common in transverse and sigmoid colon
tenia coli
mesenteric tenia : attached to mesentery
mental ténia : attached to greater momentum
Free tania: is free from any attachment (epiploic appendages attach on its right and left borders)
function of the large intestine
reabsorb water and electrolytes and create solid waste
ascending and transverse = involved in reabsorption of water and electrolytes = processing units
descending and sigmoid colon = involved in storage of faeces = storage units
rectum and anu = involved in elimination of faces = elimination units
blood supply of colon and superior rectum
appendix, caecum, ascending and transverse colon = superior mesenteric artery and vain
descending and sigmoid colon = inferior artery and vein
superior part of the rectum = superior rectal artery and vein
nerve supply of colon
midgut :
SNS = superior mesenteric ganglia and lesser splanchnic nerve
PNS = vagus nerve
hind gut
SNS = inferior mesenteric ganglia and lumbar splanchnic nerve
PNS = pelvic splanchnic nerve
histology of large intestine
goblet cells that produce mucous; helps to transport solid content
few absorptive cells (enterocytes) and villi than SI
has straight glands
Rectum
begins at S3 and is bout 12 cm long
peritoneum covers the anterior and lateral walls of the superior 1/3 of the rectum
remainder of the rectum is retroperitoneal
transverse folds of rectum
support the weight of the rectal content and lessen the urge for defecation
border between the rectum and anal canal
anorectal line (upper level of the pelvic diaphragm
line that divides the upper and lower anal canal
pectinate (dentate) line
upper anal canal
gut derivative (endoderm) and is covered by simple columnar epithelium
lower anal canal
ectodermal derivative, covered by stratified squamous epithelium
bloodd supply of the rectum
superior part of the rectum (hindgut) = superior rectal artery (branch of inferior mesenteric artery)
lower part of the rectum develop from the cloaca = middle and inferior rectal arteries (branches of bilateral internal iliac arteries
endocrine glands of pancrea
pancreatic islets = islets of langerhans
liver secretion
produces bile and drains the bile via bile duct into the mucousal surface of the duodenum
pancreas secretion
produces digestive pancreatic juice and drains the juice via pancreatic duct into the duodenum
liver function
produces and stores bile, plasma proteins, and anticoagulant substances
is involved in a variety of metabolic activities of nutrients
detoxifies harmful agents
falciform ligament
attaches the liver to the anterior abdominal wall
splits cranially into right and left coronary ligaments
round ligament
previous umbilical vein is located at the caudal margin of falciform ligament
covering of liver
visceral peritoneum = intraperitoneal
coronary ligament of liver
formed at the reflection site of the visceral peritoneum fro the liver to the diaphragm
completely surrounds the bare area
four lobes of the liver
right lobe, left lobe, caudate lobe and quadrate lobe
what separates the caudate and quadrate lobe?
porta hepatis
where is gall bladder located?
between quadrate and right lobe
what is the ports hepatis?
attachment site of the lesser momentum
blood vessels and nerves enter into the liver via ports hepatis
lesser omentum
spans between the liver and the lesser curvature of the stomach (hepatogastric ligament)
spans between the liver and the duodenum (hepatoduodenal ligament
hepatoduodenal ligament
hepatic triad
contains the bile duct, portal vein and hepatic artery proper
fetal circulation of liver
has ductus venosus of umbilical vein and umbilical vein so that umbilical blood can bypass the liver
umbilical vein becomes the ligamentum teres
ductus venous becomes ligamentum venosum
where does liver receive its blood supply from?
portal vein = oxygen poor and nutrient rich from the intestines
hepatic artery proper from cell trunk
= oxygen rich
gall bladder function
stores concentrated bile
has a cystic duct with spiral valve
blood supply to the gall bladder
cystic artery in the cystohepatic triangle of calot
histology of liver
venous blood from portal vein and arterial blood from hepatic artery mix at the liver capillaries (sinusoids)
direction of blood flow and bile flow are inverse
liver lobe
hexagonal shape
functional unit of the liver
separated from other lobules by connective tissue
composed of hepatocyte plates, a central vein and liver sinusoids
perisinusoidal space
(Disse)
portal triads contain a vein, artery and bile duct
kupffer cells (macrophages) are found in liver sinusoids
space between liver cells and sinusoids are filled with blood plasma that has leaked from the sinusoids
contain stellate cells that store fat and vitamin A
Pancreas features
retroperitoneal
pancreatic enzymes
pancreatic juice also contains sodium bicarbonate which neutralised the stomach acid present in chyme
hormones insulin and glucagon regulate blood glucose levels and are secreted into the blood stream to enter hepatic portal system
five parts of pancreas
uncinate process, head, neck, body and tail
pancreatic ducts
major pancreatic duct runs the entire length of pancreas, joins bile duct at major duodenal papilla
accessory pancreatic duct enters the duodenum separately into minor duodenal papillae
histology of the pancrea
acinus = exocrine part
islets of langerhans = endocrine part
origin of pancreas
2 buds
2 pancreatic duct: accessory duct and main duct
blood supply of the pancreas
celiac trunk
- splenic artery and gasproduodenal artery
superior mesenteric artery
- inferior gastroduodenal artery
superior and inferior pancreaticoduodenal veins
innervation of liver and pancrea
SNS = greater splanchnic nerves and celiac ganglia PNS = vagus
venous outflow of liver
hepatic portal vein is formed by superior mesenteric and splenic veins. the inferior mesenteric vein drains into the splenic vein
hepatic portal veins drains only unpaired organs
portocaval anastomoses
obstruction causes portal hypertension, blood backs up through the portal system, eventually pac through the portocaval anastomoses . they are not able to cope with large amounts of blood and become congested- varicose veins
four collateral pathways possible in GI tract
umbilical, oesophageal, anorectal, retroperitoneal
daily inflow into GIT
8 litres
daily reabsorption though GIT
SI = 6 L LI = 1.5L 92L enters)
division of the digestive system
- digestive tract
- upper = mouth to duodenum
- lower = jejunum to anus - accessory digestive organs
- glands, teeth and tongue
four major layers of the gut tube wall
- mucosa
- epithelial lining, lamina propria, muscularis mucosa - submucosa
- muscular externa
- circular inner layer
- long. outer layer - series
mesenteries of the foregut vs midgut and hindgut
foregut = ventral and dorsal mesenteries
midgut and handgun = dorsal mesentery only
cranial foregut
between oropharyngeal membrane and lung bud
formed by the pharyngeal arches and gives rise to the pharynx
caudal foregut
from the lung bud to the liver bud
thoracic part become the trachea, lung and oesophagus
abdominal part forms the stomach, superior duodenum, liver, gall bladder and pancreas
midgut
from the liveried to the 1/3rd of transverse colon
esophagus
attached with the hypo pharynx at the level of C6 to with stomach at T10
structure of the topography of the esophagus
longitudinal folds
three oesophageal constrictions
cricoid cartilage- C6
bifurcation of the trachea- T4
diaphragm at oesophageal hiatus T10
microstructure of the esophagus
stratified squamous epithelium
oesophageal glands secrete lubricant
muscular externa = upper 1/3 is skeletal, lower 2/3 is smooth muscle
lacks serosa- adventitia instead
oesophageal veins
cervical - inferior thyroid veins
thoracic- azygous and hemiazygous veins
abdominal part- left gastric veins
nerve supply of esophagus
intramural- submucosal and myenteric plexus
PNS- vagus nerves
SNS- sympathetic chain
achalasia
motor disorder of the oesophagus characterised by absence of peristalsis and impaired relaxation of the lower oesophageal sphincter
four parts of the stomach
cardia, funds, body and pyloric region
chemical digestion in the stomach
via acids and enzymes- Hcl and pepsin
little absorption of nutrients
greater and lesser omentum
lesser- attaches at the lesser curvature to the liver
greater- attache tot eh greater curvature and pancreas
cells in stomach wall
parietal cells- produce Hcl
chief cells- produce pepsin
surface mucous cells produce mucous
morphogenesis of the stomach
ventral wall and mesentery grows slower giving rise to lesser curvature
dorsal wall grows faster giving rise to the greater curvature
stomach rates around its axis 90o clockwise
left stomach becomes ventral surface supplied by left vagus nerve
right stomach becomes dorsal surface supplied by right vagus nerve
what does the falciform ligament contain?
umbilical vein that becomes the ligamentum teres
what foes the lesser omentum contain?
vessels of the liver- portal triad
what does the gastrosplenic ligament contain?
blood vessels of the stomach that branch from splenic vessels
what does the splenorenal ligament contain?
splenic artery and vein
what 4 ligaments does the spleen divide the dorsal mesogastrium into?
gastrophrenic,
gastrosplenic, splenorenal and greater omentum
artery supply of stomach
left gastric artery from celiac trunk
right gastric artery from hepatic artery proper
left gastro-mental artery from the splenic artery
right gastro-mental artery from the gastro-duodenal artery
supply of the funds of stomach
from th short and posterior gastric arteries, branches of the splenic arteries
venous drainage of the stomach
left and right gastric vein, left and right gastro-mental veins
gastric innervation
intrinsic- submucosal and myenteries
PNS- vagus nerves
sympathetic- greater splanchnic nerves
4 parts of duodenum
superior, descending, horiztonal and ascending
function of duodenum
neutralises acids of chyme from stomach
superior duodenum ligament
hepatoduodenal ligament
duodenojejunal flexure
where duodenum is continuous with the jejunum
supported by the ligament of treitz
ligament of treitz
fold containing the suspensory muscle of the duodenum
blood supply of the duodenum
celiac trunk- Branches of the gasproduodenal artery :superior pancreaticoduodenal artery
superior mesenteric artery: inferior pancreaticoduodenal artery
drainage of the duodenum
superior and inferior pancreaticoduodenal veins
ileum
has meckels diverticulum which is located in the distal ileum, around 60-100cm oral wards from the ileocecal valves
has peters patches in the terminal ileum
functional anatomy of the SI
has circular folds- valves of kerckring
has finger like intestinal villi
contains microvilli
circular folds
plicae circulars
increase SA and slow the passage of food
duplications of the mucous membrane
unlike the folds in the stomachs and LI they are permanent structures
appear more prominently in the duodenum and jejunum
microvilli
mucosa cells- lined by goblet and enterocytes
mikrovilli- located on the luminal surface of the enterocytes
lacteals- terminal lymphatic vessels in villi and transport fat metabolites and glucose whereas blood vessels in villi transport protein metabolites
density of veins in the GIT
most dense in the SI —> LI —> stomach
histology of SI
goblet cells
enterocytes
paneth cells
lymph nodes
paneth cells
located in crypts and are part of mucosal defence system
lymph nodules
located in mucosa for purposes of defence
enterocytes
most abundant cells in SI and LI
absorptive cells and contain microvilli on their apical surface
muscles of the anterolateral and posetior abdomen
anterolateral:
internal oblique, external oblique, transversus abdominus and rectus abdominus
posterior: posts major and minor, quadrates lumborum and ilacus
rectus sheath
contains anterior and posterior lamina
below the arcuate line there is no posterior lamina
between the rectus abdominis
tendinous intersections
umbilical folds
median umbilical fold contains the remanent of the urachus
medial umbilical fold contains the remnants of the umbilical arteries
lateral umbilical folds contain the inferior epigastric vessels
three types of peritoneal folds
- mesenteries- planar double layered fold of peritoneum that provide physical attachment to organs that are suspended into body cavities
omen- double layered fold of peritoneum, have a net-like structure and connect the stomach to other organs
ligaments- frequently connect organs with eachother; hence each momentum can be divided into several ligaments
lesser sac
superior wall: diaphragm and caudate lobe of liver
anterior wall= lesser momentum, posterior wall of stomach, anterior part of greater momentum
posterior wall= posterior part of greater momentum, transverse mesocolon, pancreas
left wall= spleen
right wall = liver and epiploic foramen
greater sac
extends from the diaphragm down to its lowest part in the pelvis (douglas pouch)
how do the greater and lesser sac communicate
through the mental foramen
fusion of different layers of the dorsal mesentery
the mental bursa decreases in size because the greater omentum fuses
supramesocolic compartment
contains the upper digestive organs
transverse mesocolon is the boundary
inframesocoloic compartment
contains the lower digestive organs
recesses within the supramesocolic compartment
subphrenic space- gap between the diaphragm and liver, divided by the falciform ligament
sub hepatic space - gap between the liver and right kidney
gutters
right parabolic gutter freely cominucates with the right supramesocolic spaces
phrenjicocolic ligament forms a partial barrier between the left parabolic gutter and the left supramesocolic space
movement of fluid within the inframesocolic spaces
within the right inframesocolic space is restricted inferiorly by the ileocaecal junction
fluid in the larger left inframesocolic space can flow into the pelvic cavity
