GASTROINTESTINAL SYSTEM ANATOMY II Flashcards
what are the 3 main regions of the small intestine?
- duodenum: 25cm
- jejunum: 2.5m
- ileum: 3.6m
what is the function of duodenum?
- receive acidic chyme from stomach
- receive secretions from pancreas and liver
what is the function of jejunum and ileum?
digestion and absorption
what holds small intestine in place (attach small intestine to body wall) and what does it do?
- mesentery
- allows movement but prevents tangling
what are the 4 key vessels structure of the mesentery?
- arteries
- veins
- nerves
- lymphatics
because the small intestine needs to carry out further digestion and absorption, in needs a _____1______ surface area.
to achieve it, there are 4 keyways: _________2______, ________3_________, __________4_________, and ___________5__________
1: large/huge
2: length
3: folding of intestinal wall (plicae circulares)
4: extensions of mucosa (vili)
5: extensions of epithelial cells (microvili)
what is the epithelium of small intestine?
simple columnar
what is plicae circulares? what does it originate from?
- permanent large folds of small intestine
- core submucosa with overlying mucosa
where can you find the SI villi?
surface of the plicae circulares
what is villi made of?
mucosa
what allows vili to wiggle back and forth?
muscularis mucosae
what overlaying the vili?
simple columnar epithelium
what is the core of each villus?
lamina propria
what inside the core of villi?
- lymph lacteal (absorb products of fat digestion)
- capillary network (products of protein and carbohydrate go into this)
2 key cell types of the vili?
- goblet cells for mucous secretion for protection
- columnar cells tightly packed
the absorptive cells of the small intestine (a.k.a _______1_______) have ______2______ on their _______3______ surface
1: enterocytes
2: microvilli
3: apical
what structure can you find at the base of villi?
intestinal glands/crypts
what is glycocalyx?
network of branched filaments and glycoprotein which tether enzymes
what does microvilli do?
assist contact digestion because there are enzymes attached to brush border
in the small intestine, the mucosa being the innermost layer with sheet of epithelial layer being the barrier with the lumen.
therefore it needs to be a selective barrier, to absorb what is useful to us
epithelial cell acts as the selective layer (plasma membrane) - selective permeable
has proteins to allow passages: channels, transporters
–> called transcellular pathway
what are the intercellular connections that we can find in small intestine?
- tight junctions
- adhesion belt
- gap junction
- desmosomes
tight junctions characteristics?
- very tight, but can also be loose, to ‘tightly’ control what goes through the small intestine
- small molecules may diffuse through
list all of the specialised structure that you can find on the epithelium of the small intestine? (5), among the 5, which 3 can be found in crypts?
- enterocytes: absorptive cells
- goblet cells: secrete mucous for protection
- paneth cells: granules , antibacterial enzymes
- endocrine cells: screte hormones
- stem cells: make all cell types
- epithelial, paneth and stem can be found in crypts
describe the wall of intestine from lumen inner most to outermost?
- epithelial layer covers the mucosa
- mucosa
- muscularis mucosa
- submucosa
- 2 muscle layers (circular inner and longitudinal outer)
what are the structural specialisations of the wall of the small intestine?
- plicae circulares
- villi contain lacteals and vessels
- epithelial cells along the surface and in crypts
- enterocytes with microvilli on surface
- goblet cells throughout with submucosal glands in duodenum
how is the small intestine arranged in the abdominopelvic cavity?
- duodenum (retroperitoneal) receives chyme from stomach and secretions from pancreas and liver
- jejunum
- ileum which connects to cecum
- mesentery holds SI to body wall and contains vessels
what type of blood from SI drains into the mesenteric veins? then drains into ________________?
- deoxygenated nutrient rich
- hepatic portal vein
lymph lacteal ultimately drains into the ______1_______, then the ________2________ and ________3_________
1: cysterna chili
2: thoracic duct
3: left subclavian vein
what are the functions of large intestine?
- absorption of water
- storage of feces until defecation
what are the 3 main parts of large intestine?
- cecum
- colon
- rectum
what are the 4 divided parts of colon?
- ascending colon
- transverse colon
- descending colon
- sigmoid colon
what is the location of large intestine?
- ascending and descending colon are retroperitoneal
- transvers and sigmoid colon are intraperitoneal
what is the cecum?
blind-ended pouch and location of appendix
what helps regulate the passage of material into the large intestine?
ileocecal valve
describe the appendix?
- vermiform (shaped like a worm)
- reserve of large intestine bacteria
- attached to cecum
what does an inflamed appendix be called?
appendicitis
why does large intestine wall need to be modified?
- to store and expell feces
- be lubricated (water being absorbed so it can become dry)
- allow absorption of water
what are the specialised modified structures located on the external surface of the large intestine?
- teniae coli: bands of longitudinal muscle
- haustra: series of pouches –> enhance storage (bucket-shaped)
- omental appendices: sacs of fat
describe the muscularis of large intestine and relates it to the function?
- inner circular layer
- outer longitudinal layer which forms 3 thick bands called teniae coli
–> allows for stronger contraction
what is the obvious different that we can observe on the large intestine mucosa from the small intestine mucosa?
lack of vili
mucosa of the large intestine ________1_________ to form _______2________ glands
1: invaginates
2: intestinal
what are the special structures that we can absorb on the mucosa of the large intestine?
- absorptive cells for water and salt
- goblet cells produce mucus for protection and lubrication
- invaginated intestinal glands
- lack of villi compare to small intestine
what is the rectum and what does it do?
- last part of the large intestine
- stores feces
what connects rectum to anus?
anal canal
describe the change in epithelium of anal canal and which structure mark the change?
anal column mark boundary where epithelium changes
- before: simple columnar
- after: stratified squamous
there are 2 sphincters working together to control defacation:
- _______1______ anal sphincter made up of ______2_____ muscle, therefore has involuntary control
- external anal sphincter made up of _______3_______, therefore has ________4________ control
1: internal
2: smooth
3: skeletal
4: voluntary
describe the defecation reflex process?
- movement of feces into rectum stimulates stretch receptors
- internal anal sphincter relaxes
- conscious decision to defecate –> external anal sphincter relaxes
- muscular contractions expel feces from body
what are the functions of liver?
- metabolic processes
- detoxifies blood
- produces bile
where is the liver located?
superior right quadrant of abdominopelvic cavity
what attach liver to stomach?
lesser omentum
what is the shape of the liver
wedge shaped
what is gallbladder? what does it do?
- hollow organ below liver
- stores and concentrates bile
what connects gallbladder to bile duct?
cystic duct
describe the blood supply of the liver and the percentage of each?
- receive 25% of cardiac output
- 1/3 blood supply to liver is from hepatic artery
- 2/3 blood supply to liver is from hepatic portal veins: which mean it is nutrient rich deoxygenated blood from small intestine
what structure process the received blood in liver?
hepatocyte
where does the hepatic vessels and bile duct travel within?
lesser omentum
what is the functional unit of liver called?
lobule
describe the structure of a lobule
- hexagon-shaped
- rows of hepatocytes to produce bile
- liver sinusoids between rows of cells
- bile canaliculi between cells
- central vein
- portal triad
what is portal triad?
a group of vessels consist of:
- branch of hepatic artery
- branch of hepatic portal vein
- bile duct
describe the blood flow and file production within the lobule of the liver?
- blood flows from hepatic portal vein to central vein
- during flow, being processed by hepatocytes which produce bile
- bile secreted into canaliculi and then travel to bile duct
- then central vein drains blood into hepatic vein which drains into inferior vena cava
- meanwhile bile travels to gallbladder to be stored and concentrated
- then bile duct joins the pancreatic duct at hepatopancreatic ampulla
what is bile?
a physiological aqueous solution produced and secreted by the liver. It consists mainly of bile salts, phospholipids, cholesterol, conjugated bilirubin, electrolytes, and water
