Digestive II Flashcards
1
Q
duodenum
A
- c-shapes
- upper right quadrant
- first/proximal segment of the small intestine
- becomes continuous with jejunum at duouenjejunal flexure (midline)
- major duodenal papilla is the site where bile and pancreatic secretions enter the duodenum
2
Q
jejunum
A
- middle segment of small intestine
- primary region for chemical digestion and nutrient absorption
3
Q
ileum
A
- last/distal segments of the small intestine
- distal end terminates at the ileocecal valve, a sphincter that controls the entry of materials into the large intestine
4
Q
histology of small intestine lumen
A
- mucosal and submucosal tunics are in folds called circular folds called plicae circulares
- microscopic fingerlike projections called villi ca be seen on the surface of circular folds
- microscopic fingerlike projections called microvilli can been seen on the surface of the villi
- microvilli are cytoplasmic extensions that stick up into a lumen to increase absorption, they don’t move
- greater surface area= greater absorption
5
Q
large intestine
A
- 3 sided perimeter around small intestine
- 6.5 cm in diameter but shorter vs 2.5 cm of small intestine but longer
- absorbs fluids and ions and compacts indigestible wastes and solidifies them into faces
- really good at retrieving water out of chyme
- stores the faces until defecation
6
Q
structures of large intestine
A
- cecum
- ascending colon
- transverse colon
- descending colon
- rectum
- anal canal
7
Q
cecum
A
- first part of large intestine
- blind sac located in lower right quadrant of abdomen
- ileocecal valve represents junction between small and large intestine, it stays closed until chyme is ready to exit the small intestine
8
Q
appendix
A
- vermiform appendix
- though to have a role in immunity (MALT) and maintaining bacterial gut flora
- commonly removed when blocked, inflamed, or in danger of bursting
9
Q
ascending colon
A
- originates at the ileocecal valve and ascends right side of abdoment
- more forceful peristalsis
- as it approaches the inferior border of the liver it makes a 90 degree turn toward that left side of the abdominal cavity
- this bed is called the right colic flexure (hepatic flexure) and the liver sits right on top of it
10
Q
transverse colon
A
- originates at the right colic flexure and approaches the spleen in the upper left abdominal quadrant
- suspended by the transverse mesocolon, a curtain of connective tissue that keeps it in position
- makes a 90 degree turn inferiorly at the sleep, this is the left colic flexure (splenic flexure) and the sleep is right on top of it
11
Q
descending colon
A
- originates at left colic flexure
- less forceful peristalsis
- found along the left side of the abdomen
- makes contact with ileum and terminates into the sigmoid colon
12
Q
sigmoid colon
A
- shape resembles S
- turns inferomedially and is suspended by the sigmoid mesentery
- terminates at the rectum
13
Q
rectum
A
- muscular tube that readily expands to store accumulated fecal material prior to defamation
- no absorption function
- three thick transverse fold of the rectum call rectal valves, ensure that fecal material is retained during the passage of gas
- terminates at the anal canal
14
Q
anal canal
A
- terminal few cm of large intestine
- 3 folds called rectal valves permit passage or fermentation gas while retaining fecal waste (~500ml/day), kind of like the threads on a screw
- anal column line internal surface of anal canal
- anal sinuses secrete mucin for lubrications during defecation, this needs to happen because you have absorbed all the material out of the waste and will result in bleeding if not functioning properly and could be a sign of colon cancer
- internal and external anal sphincters open and close the anal canal during defecation
15
Q
hemorrhoids
A
- blood pooling in rectal veins
- results in veins swelling
- rupturing can cause mix of blood and fecal. material causing infection
16
Q
external wall of large intestine
A
- longitudinal muscle is incomplete, forming 3 hands called coli
- they bunch of the large intestines into many sacs collectively called haustra
- small membrane-bound pouches of fat are called epiploic appendages and are only on large intestine
17
Q
histology of large intestine lumen
A
- lines with simple columnar epithelium and goblet cells which secrete mucin to lubricate fecal material
- no plicae or microvilli because you don’t need as much surface area because you are only absorbing water
18
Q
accessory digestive organs
A
- liver
- gall bladder
- pancreas
- biliary apparatus
19
Q
liver
A
- located in right quadrant of abdomen
- biggest internal organ (loaf of bread)
- comprised of 4 incompletely separated lobes
1) right lobe
2) left lobe
3) quadrate lobe
4) caudate lobe (tail)
20
Q
ligaments in liver
A
- falciform ligament separate right and left lobes, suspends the liver from the diaphragm and anterior wall
- 2 ligaments are remnants f fetal umbilical circulation: round ligament (ligumentum teres)(quadrate lobe) and ligament venous (caudate lobe)
21
Q
structures on liver forming the letter H
A
- inferior vena cave and ligaments venous form the inferior vertical parts, gall bladder and round ligaments form the superior vertical parts
- porta hepatis represents the horizontal crossbar where blood vessels (hepatic portal vein and hepatic artery proper) and lymphatic vessels, bile ducts, and nerves enter and leave the liver as part of the hepatic portal system
22
Q
hepatic portal system
A
- responsible for getting venous blood and nutrients from the digestive tract to the liver
- hepatic portal vein coming into liver, to send absorbed material to liver for processing
- substances from GI system must be processed by the liver before going to the heart for systemic circulation
- the liver receives oxygenated and deoxygenated blood at the same time
- each villus has an afferent arteriole leading into the capillary bed and an efferent venule
- each villus has its own blood supply
23
Q
lacteals
A
- lymphatic vessels in the GI tract to help absorb fatty lymph into the bloodstream
- going up the core of each villus is a lymphatic capillary
24
Q
hepatic portal system pathway
A
1) small intestine absorbs products of digestion
2) nutrient molecules travel in deoxygenated blood in hepatic portal vein to liver
3) liver monitors blood content
4) blood enters general circulation by way of hepatic vein
25
portal triads of liver
- liver is divided into hexagonal units called lobules (functional unit of liver)
- each lobule has flat plates or sheets of hepatocytes radiating out from a central vein
26
each corner of a lobule in the liver
has branches of the:
- hepatic artery: oxygenated arterial blood, normal systemic circulation like any other organ
- hepatic portal vein: nutrient-rich envois blood, different from hepatic vein
- bile duct: bile for fat emulsification
in middle in central vein that drains deoxygenated nutrient-rich blood out of liver and seeds it to systemic circulation
27
gall bladder
- embedded on inferior surface of liver
| - liver produces bile, gall bladder stores bile
28
bile
- yellow-green pigmented alkaline solution with biles salts, bile pigments (bilirubin, recycle hemoglobin), cholesterol, triglycerides, phospholipids, and electrolytes
29
bile salts
- cholesterol derivatives that emulsify fats
- emulsification breaks down large fat molecules into smaller particle to make them partially water soluble which increases surface area for lipase later in gut
- takes something non water soluble and makes it water soluble
30
gall stones
- crystalline precipitates (calculi) in gall bladder when too much cholesterols or biles salts are secreted into bile
- depends on genetics, diet, exercise etc
- may become trapped in cystic or common bile ducts during gall bladder contraction and result in extreme pain
- stones can get trapped and block removal of bile, gall bladder expands and back up bile in blood stream
- jaundice and liver cell damage can result in extreme cases
31
biliary apparatus
- network of thin ducts that transport bile from liver and gall bladder to duodenum
32
ducts of biliary apparatus
- left and right lobes of liver drain bile into left and right hepatic ducts
- left and right hepatic ducts merge to form the common hepatic ducts
- the cystic duct and common hepatic duct merge to form the common bile duct (where stones usually get stuck)
- common bile duct and main pancreatic duct enter the duodenum through the hepatopancreatic ampulla
- goes through major duodenal papilla
33
pancreas
- endocrine and exocrine function
- over 90% is exocrine tissue and 5% is endocrine
- exocrine function involves secreting digestive enzymes and bicarbonate (pancreatic juices) into the duodenum via the pancreatic duct and the hepatopancretic ampulla
34
pancreatic juices
- pancreatic juices and bicarbonate make the pancreatic juices alkaline and help neutralize acidic chyme leaving the stomach and entering the duodenum
- 500-800 ml of pancreatic juices/day
35
pancreatic secretions
- trypsinogen: zymogen for trypsin (breaks down proteins into amino acids)
- chymotrypsinogen: zymogen to chymotrypsin (breaks down proteins into amino acids)
- pancreatic lipase and co-lipase: digest lipids
- pancreatic amylase: breaks down carbohydrates
36
zymogen activation
- Trypsinogen converts to trypsin from endopeptidase, acts on chymotrypsinogen and makes it become chymotrypsin
- trypsin acts on procarboxypeptidase and makes is carboxypeptidase
