22 Flashcards
Chyme =
Acidic
Is chime acidic or basic
Acidic
What gets deleivered to the SI?
Acidic chyme
How do we protect the SI from the acidic chyme
Protection of epithelium:
- goblet cells on surface
- mucus secreting glands in submucosa (specifically in duodenum)
Neutralise pH:
- bicarbonate (HCO3-) form pancreas
How is epithelium protected in the SI?
- goblet cells on surface
- mucus secreting glands in submucosa (specifically in duodenum)
（mucus)
How is pH of acidic chyme neutralised in the SI
- bicarbonate (HCO3-) form pancreas
(duct cells pancreas)
😛
What is the first part of the SI? How can u tell?
Duodenum
- lots of glands
Three main regions of the small intestine:
- Duodenum: ~25cm
- Jejunum: ~2.5m
- Ilium: ~3.6m
Total length of small intestine
~ 6m
The length / diameter gives the SI its name
Diameter
Main role of the duodenum - what it receives
- receives chyme form stomach
- receives enzymes and bicarbonate from pancreas
- recieives bile from liver
Main function of jejunum and ilium
- digestion and absorbtion
Where is the initial segment (duodenum) of the small intestine located?
Retroperitoneal
What is the small intestine held in place by? What does it allow and what does it prevent?
Mesentary
- allows movement
- but prevents tangling
Jejuium and ilium are located
Intraperitoneal
What does the mesentary contain
- arteries
- veins
- nerves
- lymphatics
Mesentary is made of - yappage
What’s in between it and why
Double visceral layer space on inside for arteries and veins and nerves and lymphatics
- mesenteric artery and vein supply musuclairs and mucosa layer - good for carrying away nutrients absorbed in small intestine
Descriptive words for the mesentary
- shiny
- slippery
- moist
- carries vessels
- fat
What drains into the mesenteric veins? Where do these drain into?
Nutrient rich, deoxygenated blood from the small intestine enters mesenteric veins which
- these drain to the hepatic portal vein
(Only protein and carb breakdowns go into blood)
Lymphatic drainage of si (digestive tract??)
- lymph lacteals (tiny lymphatic vessels in the mucusa) ultimately drain into cisterns chyli, thoracic duct then left subclavian vein
(Breakdowns of fat)
Longest region of small intestine
Ileum
How does the structure of the small intestine relate to its function
- needs to carry out further digestion and then absorbtion so needs a hUGE surface area
How is a huge surface area achieved
- lengths
- folding of intestinal wall (plicae circulares)
- extensions of mucosa (villi)
- extensions of epithelial cells (microvilli)
What are plicae circulares and what is their structure
- permanent large folds of small intestine
- core of submucosa with overlying mucosa
How many villi and where found
- numerous
- found on the surface of the plicae circulates
What is vili made of
Mucosa
What allows vili to wiggle back and forth
Muscularis mucosae
Does vili contain blood vessels and lacteals
Yes
What is the wiggle of the vili needed for
- contact digestion (rather then just luminal digestion)
- tiny localised movements optimises digestion
What is the core of each villus made of? What does each vili contain?
- core of each virus is made of lamina propria
Contains:
- lymphatic lacteal (products of fat digestion)
- capillary network ( products of protein and carbohydrate digestion)
JUST A SINGLE LACTEAL
What kind of epithelium is of the small intestine
Simple columnar
The absorbaptivce cells (________) have _____ on apical surface
Enterocytes
Microvilli
’
What is microvilli brush boarder
Glycocalyx
What is the Glycocalyx
- glycopreoins - branched filaments that tether enzymes
(Attached to plasma membrane ?)
- anchor enzymes in place
Contact digestion; involves,es enzymes - attached to brush boarder
Two reasons for micro brush boarder.
Increase surface area for divestion
Contact digestion
The plasma membrane is a
Barrier
The plasma membrane
- selectively permeable
- has proteins
- channels
- transporter
(Allows passagE)
Pathway across Apical surface and basal surface
Trans cellular pathway
Pathway between the cells is called
Paracellular pathway
Features of tight junctions
Very tight
Small molecules may diffuse through
Location of tight junctions
As apical as possible
- right before the microvilli
Enterocytes
Absorptive cells
Goblet cells
Secrete mucous for protection
Paneth cells
granules, antibacterial enzymes
- protect against gut bacteria - look very granular
- bottom of intestinal crypt
Endocrine cells
secrete hormones
Stem cells
Make all cell types
- replicating cells pushing upwards or downwards
Stem cells Lowkey
-
This is part of the duodenum
What part of small intestine
Duodenum
IN EXAM KNOW HOW TO DRAW AND EXPLAIN
What is at the end of the small intestine before the large intestine
Ileocecal valve
What does the iliocecal valve do?
- regulates the passage of material into the large intestine
Once we go from small to large intestine we can’t…
Go back
Large intestine is for
Storage and absorption of water and salts
How is the small intestine arranged in the abdominopelvic cavity
Duodenum (retroperitoneal) receives chyme from stomach & secretions from liver & pancreas. Jejunum, then ileum, which connects to cecum. Mesentery holds SI to body wall and contains vessels.
What are the structural specialisations of the
wall of the small intestine?
Plicae circulares (permanent folds). Villi, contain lacteals and vessels for absorption, and several epithelial cells along surface and in crypts. Enterocytes have microvilli on surface.
Goblet cells throughout, with submucosal glands in duodenum.
What are their roles in digestion and absorption
Large SA needed for effective digestion and absorption. Movement of villi, and glycocalyx on microvilli important for digestion.
Compare and contrast the structure and function of the stomach and small intestine. Include modifications to the gut tube for these two organs
Do this bro its in exam promise
