Anatomy of the Gut Flashcards
What are the 4 layers of the gut tube (from innermost to outermost)?
- Mucosa (innermost)
- Submucosa
- External muscle layers
- Serosa (outermost)
What are the layers of the muscosa? (innermost → outermost)
- Epithelium (innermost)
- Lamina Propria
- Muscularis Mucosa
- Submucosa
What is the function of the epithelial layer of the mucosa?
- selectively permeable barrier
- transport and digestion of food
- promotes absorption
- produces hormones
- produces mucus
What is the function of the Lamina Propria of the mucosa?
- lymphoid nodules and macrophages
- produces antibodies - mainly IgA
What is the function of the Muscularis mucosae of the mucosa?
- smooth muscle in different directions
- keeps epithelium in contact with gut contents
- keep crypt contents dynamic
What is the function of the submucosa of the mucosa?
- dense connective tissue, blood vessels, glands and lymphoid tissue
- contains Meissner’s (submucosal Plexus)
Explain the change in gut epithelial cells along the legnth of the digestive tract
Oesophagus → Stratified Squamous cells
In between → Simple Columnar
Distal Anus → Stratified Squamous
What are enterocytes?
- Simple columanar epithelial cell that line villi
- 1 cell thick
- up to 3,000 microvilli per enterocyte
- contains digestive enzymes
What are goblet cells and how are they distributed throughout the gut?
- Mucus producing cells scattered between enterocytes
- Increase in number from duodenum to colon
Why is mucus essential for gut epithelia?
Protect epithelia from
- Friction (acts as a lubricant)
- Chemical damage (acidic environment)
- Bacterial inflammation
What are foveolar cells?
Gastric muscous cells, dominant in the stomach
- line gastric mucosa/ pits
- secrete mucus and HCO3 to protect stomach from acidic contents
What are rugae and why are they needed?
Temporary stomach folds, allow distention of the stomach
Where in the GI are Villi found?
small intestine
Where are crypts found within the GI?
Small and large intestine
What cells are found in crypts and why?
- Stem cells → replace gut epithelia every 2-3 days
- Paneth cells → maintain stem cells by secreting anitbacterial proteins
- Enteroendocrine cells → produce gut hormone
Describe the layers of the abdominal wall
Describe the arrangement of the anterolateral muscles of the abdminal wall
- External oblique - hands in pockets direction of fibres
- Internal oblique- perpendicular to external fibres
- Transverse abdominis- horizontal plane
What is the rectus sheath?
An aponeurosis of lateral abdominal muscles that surrounds the rectus abdominis
What is the arcuate line and what is its significance?
Located half way between umbilicus and pubic crest
- Above line- all aponeurosis equally distributed around rectus abdominis
- Below line-all aponeurosis run anterior to rectus abdominis
Briefly explain the peritoneal cavity
- a mesothelium lines cavity of flattened squamous epithelium
- produces lubricating fluid
- envelopes certain viscera and lines the cavity wall
- No organs are in the peritoneal cavity
Differentiate between intraperitoneal and retroperitoneal viscera
- Intraperitoneal → viscera surrounded by peritoneal cavity
- Retroperitoneal → viscera in abdominal wall but behind ther peritoneal cavity
What are mesentries?
- Double folds of peritoneum that attach viscera to posterior abdominal wall
- Contain
- blood vessels
- lymph vessles
- nerves
- fat
What is the difference betwene parietal and visceral peritoneum?
- Parietal = in contact with abdominal wall
- Visceral= off the abdominal wall and surrounding intraperitoneal viscera
