Lecture 18 - Digestive 2 Flashcards
Parts of the small intestine
*DJ ILLEUM*
- > duodenum
- > jejunum
- > illeum
Characteristics of Duodenum
- > some chemical breakdon occurs in this structure
- > first/proximal segement of the small intestine
- > becomes contiuous with jejunum at the duodenojejunal flexure
- > the duodenal papilla is the site where bile and pancreatic secretions enter the duodenum
Jejunum
- > middle segment of the small intestine
- > primary region for chemical digestion and nutrient absorption
Illeum
*NOT ILLIUM*
- > last/distal segemtent of the small intestine
- > site for absorption and digestion
- > illeum/small intestine ends and connects to large intestine at the ileocecal valve (sphincter that controls the entry of materials into the LI)
Explain the histology of the small intestine
- > the mucosal and submucosal tunics are thrown folds called the plicae circulares
- > the plicase have microscopic projections on their surfaces called villi
- > the surfaces of villi house even smaller projections called microvilli
*this increases the surface area of SI to increase absorption*
functions of the large intestine
- > absorbs fluids and ions and compacts indigestible waste and solidifies them into feces
- > stores the feces until defecation (poopoo)
Diameter of small vs large intestine
LI - > 6.5cm
SM - > 2.5cm
Which structures make up the large intestine
- > cecum
- > ascending colon
- > transverse colon
- > descending colon
- > sigmoid colon
- > rectum
- > anal canal
Characteristics of the cecum
- > first part of large intestine
- > pouch of terminal end of LI which houses appendix
- > illeocecal valve represents junction between small intestine and large intestine
Vermiform Appendix
- > aka. appendix
- > though to have a role in immunity (MALT)
- > theorized that it has a role in maitaining/replenishing gut flora (bacteria)
- > commonly removed when blocked, inflamed or in danger of bursting
Dangers of a burst appendix
- > fecal matter or bacteria can get lodged in the small lumen which can leak into body if burst causing sepsis
- > it is warm, moist and vascular; perfect condition for bad bacterial growth
Characteristics of the ascending colon
- > originates at the ileocecal valve and ascends right side of abdomen
- > uses very strong peristalsis
- > as it approaches the inferior border, it makes a 90 degree turn towards left side of the abdominal cavity and leads into transverse colon (this bend is called the right colic flexure; hepatic flexure)
Characteristics of the transverse colon
- > originates at the right colic flexure (hepatic flexure)
- > suspended by curtain-like connective tissue transverse mesocolon
- > turns 90degrees down into decending colon at left colic flexure (splenic flexure)
Characteristics of the descending colon
- > originates at the left colic flexure
- > found along left side of abdomen
- > makes contacts ileum and terminates into the sigmoid colon
How does the large intestines/ colons move feces
with peristalsis
- > acending uses very storng peristalsis
- > tansverse, descending and sigmoid colons use a weaker form
Characteristics of the sigmoid colon
- > shaped like and S
- > turns inferomedially and is suspended by sigmoid mesentery
- > terminate as the rectum begins
characteristics of the anal canal
- > anal columns line the interal surface of the anal canal
- > anal sinuses secrete mucin for lubrication during defication
- > internal and external anal sphincters open and close the anal cana during defication
lobes of the liver
- > right lobe
- > left lobe
- > quadrate lobe
- > caudate lobe
ligaments of the liver
- > falciform ligamnet separates the right and left lobes, suspends the liver from the diapragm and anterior wall
- > two ligaments are remnants of fetal umbilical circulation
- round ligament (free edge of falciform) (ligament teres)
- ligamentum venosum
External structures of the liver
- > several structures collectively make the shape of the letter H
- > inferior vena cava and ligamnetum venosum form the inferior vertical parts
- > gall bladder and round ligament form the superior vertical parts
- > the porta hepatis represents the horizontal crossbar;
• this is where the 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 protal system
Hepatic Portal system
- > responsible for getting venous blood and nutrients from the digestive tract to liver
- > substances from GI system must be processed by the liver before going to the heart for systemic circulation
- > the liver therfore receives both oxygenated and deoxygenated blood at the same time
how does the hepatic protal system work; specifically with the small intestine
- > each villus has an afferent arteriole leading into the capillary bed, and an efferent venule
- > uses lacteals
lacteals - > lymphatic vessels within the GI tract to help absorb fatty lymph into the blood stream
Histology of the liver
- > the liver is divided up into hexagonal units called lobules
- > each lobule consists of hepatocytes radiating out of a central vein
- > at each corner of the lobule is a portal triad with brances of the
1. hepatic artery
2. hepatic portal vein
3. bile duct
path of biliary apparatus
- > left/right lobes of the liver drain bile into left/right hepatic ducts
- > L/R hepatic ducts merge to form the common hepatic ducts
- > the cystic duct and common hep. ducts merge to form the common bile duct
- > the common bile duct and main pancreatic merge at the hepatopancreatic ampulla
- > pancreatic juices and bile enter the duodenum through the duodenal papilla
pancreatic endodrine and exocrine cells
Endocrine - > islet of langerhan cells (produces insulin)
Exocrine - > acinar cells (produce and transport digestive enzymes)
Main vessels of the pancreas
- > main pancreatic duct
- > accessory pancreatic duct
- > hepatopancreatic ampulla
- > major duodenal papilla
