1b.) Basic Anatomy Flashcards
State the four layers of the GI tract innermost to outermost
State 4 roles of the epithelial layer of the mucosa
It is a selectively permeable barrier which:
- Facilitates transport and digestion of food
- Promotes absorption
- Produces hormones
- Produes mucus
State the three layers of the mucosa innermost to outermost
- Epithelium
- Lamina propria
- Muscularis muosae
State the main role(s) of the lamina propria in the mucosa
Has lots of lymphoid tissue and macrophages to produce antibodies to protect against bacterial or viral infection
What antibodies are mainly produced by lamina propria of mucosa and why?
IgA as reistant to proteases
Label the following image
State 2 roles of the muscularis mucosa layer of the mucosa
Layers of smooth muscle orientated in different directions which:
- Keep epithelium in contact with gut contents
- Help keepy crypt contents dynamic
State the contents of the submucosa
- Dense connective tissue
- Blood vessels
- Glands
- Lymphoid tissue
- Submucosal (Meissner’s) plexus
Describe the arrangement of muscle fibres in the muscularis propria and state what is found betwen the two layers
- Outer longitudinal muscle (shorten gut)
- Myenteric (Auerbach’s plexus)
- Inner circular muscle (peristalsis)
State 3 contents of the serosa
- Blood vessels
- Lymph vessels
- Adipose tissue
The serosa is continuous with mesenteries; true or false
True
Give a brief overall description of layers, and sublayers, of the GI tract
What epithelia is found in the alimentary canal? CLUE: does it change as you go down the alimentary canal
- Stratified squamous in oesophagus and distal anus
- Everything inbetween is simple columnar
What type of epithelial cell is an enterocyte and what does it do?
Simple columnar epithelial cell that absorbs
Why must blood vessels and lymphatics lie immediately below enterocyte in the lamina propria?
Nutrients must be transported through both apical and basolateral membrane to be absorbed
State 3 anatomical features of small intestine to increase surfacea area
- Plicae circulares (permanent folds)
- Villi
- Microvilli
What is meant by the brush border?
The microvilli (increases surface area but also contains digestive enzymes)
Where do you find goblet cells in GI tract?
Scattered between enterocytes increasing in number from duodenum to colon
Why is nucleus of a goblet cell at the base?
Mucus compresses nucleus
Mucus protects epithelia from what three things?
- Friction (it is a lubricant)
- Chemical damage (environment can be acidic)
- Bacterial inflammation (physical barier)
Where are foveolar cells found and what is their role?
Foveolar cells lien gastric mucosa and secrete mucus, which contains HCO3, which acts as a barrier against stomach acid
What are the permanent folds in the small intestine called?
Plicae circulares
What are rugae and why are they needed?
Rugae are temporary folds in the stomach which allow it to expand
What are haustra and where are they found?
Haustra are small pouches/sacculations which gives colon segmented appearance. As a result of contraction of longitudinal muscle
What are crypts, where are they found and what is the function of crypts?
Pits found in the small and large intestine that contain specialised cells.
Function:
NOTE: also called crypts of Lieberkuhn or intestinal glands
State 3 cells found in crypts
- Stem cells
- Paneth cells
- Enteroendocrine cells
State the role of stem cells found in crypts
Constantly divide to replace epithelia every 2-4 days
State the role of paneth cells in crypts
Secrete antibacterial proteins to protect stem cells
State the role of enteroendocrine cells in the crypts
Secrete hormones that control function of the gut e.g. gastrin, cholecystokinin, secretin
Briefly describe the arrangement of stem cells, paneth cells and enteroendocrine cells in crypts
Give 3 examples of glandular tissue in the gut
- Salivary glands
- Pancreas
- Brunners glands (duodenum- neutralisation & osmotic role)
State ALL layers of the abdominal wall starting from outermost to innermost
- Skin
- Fascia/fat
- Superficial
- Deep
- External oblique
- Internal oblique
- Transverse abdominis
- Rectus abdominis (middle of three above)
- Transversalis fascia (beneath muscles)
- Peritoneum
Describe the direction of the fibres in the:
- External oblique
- Internal oblique
- Transverse abdominis
- Rectus abdominis
Do the external oblique, internal oblique and transverse abdominis have aponeurosis’?
Yes… they envelop the rectus abdominis muscle- called rectus sheath
What is the arcuate line and where is it?
- Below the arcuate line the rectus sheath only goes anterior to the rectus abdominis wherease above the arcuate line the rectus sheath goes both anterior and posterior to the rectus abdominis.
- Roughly halfway between umbilicus and pubic crest
What is the tendinous portion betwen the two halves of rectus abdominis called?
Linea alba
What is the peritoneal cavity made of?
Mesothelium lined cavity with flattened simple squamous epithelium, a basement membraneand dense irregular connective tissue
There are two types of peritoneum; describe these and where they are found
- Visceral: envelops viscera
- Parietal: lines cavity wall
What does the peritoneum produce?
Lubricating fluid
What are intraperitoneal viscera?
Viscera that are enveloped in peritoneum that has projected off cavity wall (visceral peritoneum)
What are retroperitoneal viscera?
Viscera that are not enveloped and lie posterior to peritoneal cavity
What is a mesentery? What does it contain? What is it’s function?
Double fold of visceral peritoneum that attaches certain viscera to the posterior abdominal wall. Contains blood vessels, lymph vessels, nerves, fat. It anchors abdominal organs in place whilst still allowing some movement and provides conduit for blood vessels, lymphatics etc..
State which viscera are enveloped by peritoneum and hence attached to posterior abdominal wall (6)
- Jejenum
- Ileum
- Appendix
- Transverse colon
- Sigmoid colon
- Rectum
Is the peritoneal cavity closed in both males and females?
Closed in males, open at entrance to fallopian tubes in females
Where is the peritoneal cavity?
Space between parietal and visceral peritoneum
Is the GI tract an external environment? What are the implications of this?
External environment as mouth and anus link it to the external environment. Implications:
- Infection risk/entry of pathogens
- Easy examination without incisions
- Allows substances to easily get in and out of body which aids it’s function
What is the alimentary canal?
The entire passage along which food passes down from mouth to anus
What is the function of the peritoneal cavity?
- Peritoneal cavity contains small amoutn of peritoneal fluid which reduces friction betwen organs as they are dynamic when working
- Helps keep abdominal organs in place
Describe the innervation of the visceral and parietal peritoneum and the implications of this when it comes to pain
- Visceral: has same autonomic nerve supply as the viscera it covers hence pain is poorly localised. Pain is referred to dermatomes which are supplied by same sensory ganglia or spinal cord segments
- Parietal: has same somatic nerve supply as the region of the abdominal wall that it lines hence pain is well localised
State the abdominal viscera which are retroperitoneal
- Suprarenal glands
- Aorta and IVC
- Duodenum (except proximal 2cm)
- Pancreas
- Ureters
- Colon (ASCENDING AND DESCENDING ONLY)
- Kidneys
- Esophagus
- Rectum
SAD PUCKER
For the greater and lesser omentum state:
- What they are
- Where they descend from and attach back to
Greater omentum: four layers of visceral peritoneum which descends from greater curvature of stomach and proximal duodenum and folds back up to attach to anterior surface transverse colon
Lesser omentum: double layer of visceral peritoneum which attaches from lesser curvature of stomach and proximal duodenum to the liver
For each of the muscles of the abdominal wall state the nerve supply
- External oblique: subcostal nerve (T12)
- Internal oblique: subcostal nerve (T12) and L1 spinal nerve
- Rectus abdominis: subcostal nerve (T12)
- Transversus abdominis: subcostal nerve (T12) and L1 spinal nerve
Describe the 6 different portions of the mesentery
- Mesentery of small intestine: mobile but connects small intestine to posterior abdo wall
- Right mesocolon: flattered to posterior wall
- Transverse mesocolon: mobile
- Left mesocolon: flatted to posterior wall
- Mesosigmoid: mobile (small section flatted to posterior abdo wall)
- Mesorectum: anchors rectum through pelvis
State the action of the external oblique muscle
- Rotates vertebral column to opposite side
- Bends trunk at same side
State the action of the internal oblique muscle
- Rotation and lateral flexion of trunk on ipsilateral side
State the action of the transversus abdominis muscle
Rotation, flexion and lateral flexion of the trunk
State actions of the rectus abdominis muscle
- Flexion of trunk
- Stabilization of pelvis
What is a peritoneal ligament? State the 4 peritoneal ligaments you need to be aware of
Double fold of peritoneum that connects viscera together or connects viscera to the abdominal wall.
- Falciform ligament (attaches liver to front body wall and splits liver into left and right lobe)
- Lesser omentum (stomach to liver)
- Gastro-colic ligament (stomach to transverse colon)
- Gastro-splenic ligament (stomach to spleen)
NOTE: gastro-colic and gastro-splenic ligament make up the greater omentum
State the 9 regions of the abdomen and where each of the following organs is found (may want to draw it):
- Liver
- Gallbladder
- Pancreas
- Spleen
- Kidneys
- Stomach
- Duodenum
- Jejenum
- Ileum
- Caecum
- Appendix
- Ascending
- Transverse
- Descending colon
- Sigmoid colon
What is the connection between greater and lesser sac called?
Foramen of Winslow/Epiploic foramen
