23 Flashcards
Essay question: compare and contrast the structure and function of the stomach and small intestine. Include modifications to he gut tube for these two organs.
Stomach two functions and how they relate to structure
Stores food:
- Rugae: temporary folds of submucosa
Digests - mechanically and chemically :
- exerts oblique layer of muscularis for motility
- pyloric sphincter restricts entry to small intestine
- acidic environment - parietal cells
- pepsin - chief cells
- gastric glands
- mucus for protection
Small intestine two functions and how they relate to strucuture
Receive chyme:
- mucus for protection (submucosal glands in duodenum)
- bicarbonate (and enzymes) from pancreas
- bile from liver
Digestion and absorbtion:
Huge surface area
- ~6m
- plicae circulares: permanent folds, core of submucosa
- Vili: mucosa, contain lacteal and BVs
- Microvili: enerocytes
The role of the stomach is to store and digest food. Temporary folds of the submucosa called rugae allow expansion, while the acidic environment is created by parietal cells found in gastric glands. Alongside these cells are chief cells that produce pepsinogen, the inactive form of pepsin, which digests protein. The stomach is protected by a layer of mucus produced by numerous goblet cells at the enterance to these glands. Motility in the stomach mechanically digests food, aided by an additional inner oblique layer of muscle. The pyloric sphincter, a thickened region of smooth muscle, control entry of chyme into small intestine.
The small intestines role is to further digest and absorb nutrients. As chyme is acidic, the initial part of the small intestine, the duodenum, is protected by mucus from submucosal glands, and the acid is neutralised by bicarbonate from the pancreas.
Additional secretions - enzymes from the pancreas and bile from the liver - enter the small intestine here. Luminal contact and digestion occurs through mixing secretions with chyme along the ~6 length of the small intestine. The surface area is maximised by permanent folds of the submucosa called plicae circulares. The mucosa has extensions called vili and the enterocytes which line the surface have microvili to further increase surface area. Nutrients are absorbed into the blood vessels and lacteals within the vili
What is the function of the large intestine?
- absorbtion of water (and salts)
- storage of feces until defecation
What dies the large intestine consist of?
Consists of cecum,
colon, and rectum
What is the colon divided into ?
Colon divided into:
• Ascending
• Transverse
• Descending
• Sigmoid
How many meters long is LI
- 1.5 m
• Ascending • Transverse • Descending • Sigmoid
…are retroperitoneal or intraperitoneal
• Ascending and
descending colon
are retroperitoneal
• Transverse and
sigmoid colon are
intraperitoneal
Barium enema enables…
… imaging to access function
Structure of the caecum
• Blind-ended pouch
Where is the location of the appendix
The cecum
What dies the ilieocecal valve do?
• Ileocecal valve regulates the passage of material into the
large intestine
Another name for the appendix
Vermiform appendix (worm shaped varies from a couple cm long to 30cm long
Function of the appendix
• Reserve of large intestine bacteria
(Don’t need it to live)
Attached to?
• Attached to cecum
WhAt happens if the appendix becomes inflamed?
Appendicitis
Appendicitis
When appendix becomes inflamed
Large intestine wall needs to be modified to:
• Store feces
• Expell feces during defecation
• Be lubricated
• Allow absorption of water
3 structural features of the LI
Teniae Coli
Haustra
Omental appendices
Teniae Coli
- bands of longnitudanal muscle
Haustra
• Series of pouches
Omental appendices
• Sacs of fat
Features of the large intestine muscularis
- inner circular layer is a complete circular
- outer longitudinal layer forms three thick bands - teniae coil
- allows for stronger contraction
Large intestine mucosa
- lack of villi
- mucosa invaginates to form intestinal glands
- absorptive cells for water and salt
- goblet cells produce mucus for protection and lubrication
(Needs intestinal cells to absorb water and salts and goblet cells for mucus - lubrication)\
(Lots of intestinal glands for large SA for goblet cells - packed)