2. Setting the Scene (Anatomy) Flashcards
What are the two main types of the epithelial cell found in the GI tract and where r they found?
Stratified squamous in oesophagus and distal anus
o Everything in between is simple columnar
Function of stratified squamous non keratinised epithelium found in GI tract? Hint: think about where it’s found specifically
Resists abrasion/stress (physical + chemical). Hard food and faeces bcs found at mouth and distal anus.
Non keratinised means it SECRETES MUCUS to protect + lubricate.
Describe the enterocytes and their function
A simple columnar epithelial cell that absorbs
o Predominant cell of small intestine and colon
o One cell thick!
o Need to transport nutrients through
- Apical membrane
- Basolateral membrane
o Blood vessels/lymphatics lie immediately below the
enterocyte (in LP)
What is a specialised feature of enterocytes?
◦ Microvilli (collectively termed brush border)
Where are goblet cells found and how do they get their name?
o Scattered in between enterocytes
o Increasing in number from duodenum to colon
o They get their name from a narrow base and larger
apical size
Why is the nucleus of a goblet cell at its base?
Mucus pushes it down to the base
What does the mucus from goblet cells protect the epithelia from?
o Friction (acts as lubricant)
o Chemical damage (acidic environment)
o Bacterial inflammation (forms physical barrier)
WHat are mucous producing cells in the stomach called and what else do they produce?
Gastric surface mucous cells (foveolar cells)
o Line gastric mucosa/gastric pits
o Secrete mucus/HCO3 that forms barrier to stomach acid
Describe foveolar cells
o simple columnar epithelium
o divided in two groups:
- surface mucous cells, which line the surface and the gastric pits
- mucous neck cells, which are a part of the neck of gastric glands
What are the permanent folds in the intestine called?
Plicae circulares or vulvulae conniventes
What two factors of the small intestines increase surface area?
permanent fold
villi
microvilli
What are the folds in the stomach called and what do they allow?
Rugae, allows the stomach to be easily expandible
What are haustra?
Sacculations in the large bowel
Where are crypts found?
In small and large intestine
o Sometimes known as crypts of Lieberkuhn/intestinal glands
What specialised cells are found within the crypts and what are their functions?
o Stem cells
o Paneth cells
o Enteroendocrine cells
How does the gut maintain its epithelial barrier to protect from stomach acid?
Contains stem cells that replace epithelia every 2-4 days
What is the role of a Paneth cell?
Secretes antibacterial proteins, which protect stem cells of gut
Found at the base
What are Brunner’s glands and where are they found?
Proximal duodenum - secrete alkaline mucoid material into crypts to neutralise acidic chyme from stomach.
Function of columnar cells found in the colon (large intestine)? Why do they contain lots of ATPase pumps?
Extract final amounts of water from faecal material. Does this against a strong conc grad so requires a lot of energy. Active fluid transport.
WHat are the 4 layers of the gut tube?
Mucosa (innermost)
o Submucosa
o External muscle layers
o Serosa (outermost)
What are the layers of the mucosa?
epithelium, lamina propria, muscularis mucosa
What is the function of the epithelial layer of mucosa?
o Selectively permeable barrier o Facilitate transport and digestion of food o Promote absorption o Produce hormones o Produce mucus
What is contained within the lamina propria and what does it produce?
o Lots of lymphoid nodules and macrophages
o Produce antibodies (mainly IgA which is resistant to
proteases)
Protect against bacterial/viral invasion
What is the muscularis mucosae?
o Layers of smooth muscle orientated in different
directions
o Keeps epithelium in contact with gut contents
How does the muscularis mucosa prevent infection?
Helps keep crypt contents dynamic to prevent stasis. Stasis would result in infection
What is contained within the submucosa?
Dense connective tissue, blood vessels, glands, lymphoid tissue, submucosal (Meissner’s) plexus
What is contained within the muscularis externa?
Inner circular muscle o Myenteric (Auerbach’s) plexus Outer longitudinal muscle`
What is contained in the serosa?
o Blood and lymph vessels and adipose tissue
o Continuous with mesenteries
What are the crypts found between?
Found between villi
What is the peritoneal cavity?
Mesothelium lined cavity
o Flattened simple squamous epithelium
o Basement membrane
o Dense irregular connective tissue
Describe the function of the peritoneal cavity
o Produces lubricating fluid
o Envelopes certain viscera (projects off cavity wall)
What are the viscera that are enveloped by the visceral peritoneum called?
Intraperitoneal viscera - not inside peritoneal cavity but enveloped by it
What is the name of the part of peritoneum that lines the cavity wall?
parietal peritoneum
What are retroperitoneal viscera?`
Viscera that are not enveloped and lie posterior to
peritoneal cavity - only anterior surface covered by peritoneum
What does the peritoneal cavity contain?
empty - small amount of fluid - reduces friction between structures
Given that the peritoneal cavity is empty, describe, in basic terms, how intra-peritoneal structures receive their blood supply from the retro-peritoneal space.
Mesentery
What is the mesentery?
A double fold of the peritoneum that attaches certain viscera to the posterior abdominal wall
Which structures contain a mesentery?
◦ Jejenum ◦ ileum ◦ Appendix ◦ Transverse colon ◦ Sigmoid colon ◦ Rectum
Function of mesentery?
Blood supply to intraperitoneal structures from retroperitoneal space bcs peri cavity is empty.
- attaches structures to abdominal wall and fixes them in a fixed postition
What are the retroperitoneal structures? Name them (hint : SAD PUCKER)
S = Suprarenal (adrenal) Glands. A = Aorta/IVC. D =Duodenum (2nd - 4th parts) P = Pancreas (except the tail) U = Ureters. C = Colon (ascending and descending parts) K= Kidneys. E = eosophagus. R = rectum
What are omenta?
Specialised regions of peritoneum
What structure is the greater omentum derived from?
Dorsal mesentery
What structure is the lesser omentum derived from?
Ventral mesentery
What is the peritoneal ligament?
double fold of peritoneum connecting viscera
What are the layers of the abdominal wall?
Skin, Fascia/fat (superficial/deep), 3x anterolateral muscles, rectus abdominis, transversalis fascia, peritoneum
What are the 3 anterolateral muscles of the abdominal wall?
External oblique, internal oblique, transverse abdominis
Describe the direction in which external oblique, internal oblique and transverse abdominis runs?
External = “hands in pockets”
Internal =mediosuperiorly
Transverse = towards linea alba (midline)
Actions of external oblique muscle
Compress abdominal viscera
Flex trunk
Contra-lateral rotate trunk - rotate core to opposite side of muscle
Origin and insertion of external oblique?
Origin 5-12th rib
Inserts iliac crest, inguinal ligament, linea alba
Actions of internal oblique?
Ipsilateral rotation of trunk
Compress abdominal viscera
Flex trunk
Origin and insertion of internal oblique?
origin: lateral portion of inguinal ligament, iliac crest, thoracolumbar fascia
insert: lower 3/4 ribs, linea alba via aponeorosis, pubic crest
Actions of transverse abdominis?
Core stability
Compress abdominal contents
What is an aponeurosis?
o Thin sheet like tendon
These have them: o External oblique o Internal oblique o Transverse abdominis These lateral muscles have aponeurosis that envelops the midline rectus abdominus muscles
What is the rectus sheath?
Name of the sheet that all the aponeurosis of the anterolateral abdo muscles makes
What nerves innnervate anterolateral muscles of abdominal wall (external,internal oblique and transverse abdominis)?
Anterior rami of T7-12. Internal and transverse also L1
Anatomical significance of the arcuate line?
Above the line, the internal oblique muscle splits to envelop the muscle w external oblique going above and the transverse abdominis going below.
Below the line, all 3 muscles tendons run above the rectus abdominis muscle
Where is the arcuate line found?
Halfway between the umbilicus and pubic symphysis
Above the arcuate line, the aponeuroses of which muscles envelop the anterior surface of the rectus abdominis muscles?
External oblique
Internal oblique
Below the arcuate line, the aponeurosis of which muscles envelop the anterior surface of the rectus abdominus muscles?
All 3 : external oblique
internal oblique
transverse abdominus
What is the lower limit of the posterior rectus sheath and what is then posterior to the rectus abdominis?
Arcuate line, Roughly half way between umbilicus and pubic crest. Transversalis fascia then lies posterior.
What separates the right and left rectus abdominis?
Linea alba (part of the rectus sheath)
What is the lateral border of the rectus abdominis?
Linea semilunaris
Which structures are contained within the peritoneal cavity? Ie intraperitoneal structures
Spleen
Liver
Transverse and sigmoid colon
