Digestive System II Flashcards
Describe the location of the stomach and where it gets its vasculature?
- Intraperitoneal
- In LUQ (left upper quadrant)
- Vasculature from the celiac trunk
How does the stomach contribute to digestion?
- Mechanical breakdown
- mixing and churning via segmentation (contractions of muscular wall)
- Chemically/enzymatically
- secreted acids and enzymes
Mixed bolus and gastric juices is called:
Chyme - viscous, acidic, soupy mixture
What mesentery is associated with the greater curvature of the stomach?
Greater omentum = forms “apron”
What is the greater omentum?
What is found here?
Mesentery from the greater curvature of the stomach to the transverse colon
- Protective layer
- Blood, nerves and lymphoid tissue
- Lipid deposition for temp control
- Immunological function
- Moves easily = follows infection within the perotineum
Why is the upper portion of the stomach given the term “cardiac”
Close to heart
Shares dermatome with heart = sensory implications (eg heartburn)
What are the four major parts of the stomach as mentioned in lecture?
- Fundus
- Cardia
- Pyloric Canal (Pylorus)
- Body
What type of epithelium makes up the stomach? And why?
Simple Columnar Epithelium - absorption
What are the three layers of smooth muscle in the stomach?
- Inner oblique
- middle circular
- outer longitudinal
What are the folds within the stomach called? What is their purpose?
Rugae
- Allow stomach to stretch
The surface of the Rugae is called the ______ and is where we would find:
The surface of the Rugae is called the Gastric Pit and is where we would find:
- Stem cells
- 1 cell layer of Simple Columnar Epithelium
Each gastric pit is associated with ______ which produce the HCl and enzymes
Each gastric pit is associated with Gastric glands (many) which produce the HCl and enzymes
Label the Rugae:
- Gastric pit
- Mucosa
- Muscularis
- Submucosa
- Gastric Gland
- Serosa
What are the 5 Gastric Gland secretory cells mentioned in lecture?
- Surface Mucous Cell
- mucous
- Mucous Neck Cell
- mucous
- Parietal Cell
- HCl
- Chief Cell
- pepsin, lipase
- Neuroendocrine cell
- gastrin
What is the difference between the mucous produced by the surface mucous cells and the mucous produced by the mucous neck cells?
- Surface mucous cell:
- Thick alkaline mucous
- Mucous Neck Cell
- Higher water content
Which gastric gland-secretory cells secrete HCl?
Parietal Cells
Which Gastric gland - secretory cell secretes pepsin and lipase?
Chief cell
What is important about the type of enzymes produced by chief and parietal cells?
Chief cells secrete pre-enzymatic enzymes. Not able to digest until they mix with the mucous within the mucous neck cell = activates enzymes/acid
PROTECTION - prevents digestion of “self”
What hormone is released by the neuroendocrine cell in the gastric gland?
Gastrin - stimulates chief and parietal cells
What are the three parts of the small intestine?
- Duodenum
- associated with stomach, liver and pancreas
- Final digestion
- Jejunum
- Most absorption
- ileum
- Remaining absorption
What is present in the small intestine that makes it especially good at absorption? (3)
- Circular folds called plicae circulares
- villi
- microvilli
The small intestine is mostly ______ (location) with the exception of the duodenum
The small intestine is mostly intraperitoneal (location) with the exception of the duodenum
The small intestine extends from the ______ of the stomach to the ______ (beg of L. intestine) and is found in _______ quadrant(s)
The small intestine extends from the pyloric orifice* of the stomach to the *ileocecal valve (beg of L. intestine) and is found in all 4 quadrant(s)
The duodenum receives ____ from the stomach and secretions of the _____ and _____ via the ______
The duodenum receives chyme from the stomach and secretions of the pancreas and gallbladder via the gall bladder
What occurs in the duodenum?
Digestion of fat, proteins and sugars
What is the vasculature of the duodenum?
Anastomosis of the celiac and SMA (superior mesenteric a.) branches
recall: anastomosis = connection/joining between vessels
Which structure provides protection for the small intestine against the acidity of the chyme? How?
Brunner’s Glands
- Provide abundant alkaline mucous to neutralize the acidity of the chyme
- Pancreatic buffers contribute to neutralization
Where are Brunner’s glands found?
In the submucosal layer (connective tissue layer of duodenum)
What does chyme in the duodenum stimulate?
Stimulates mucosa to produce hormones (secretin and cholecystokinin -CCK) to relax sphincter = release pancreatic juice and bile
What is bile?
Where is it stored?
Bile is a byproduct of liver filtration that aids in the digestion of lipids (when combined with salt)
stored in the Gallbladder
Bile and pancreatic juices enter the Duodenum through the:
Hepatopancreatic ampulla
What does the pancreas produce? (ie what is found in the pancreatic juices entering the duodenum)
Enzymes that aid in the digestion of fats, proteins and carbs + bicarbonate buffer
Describe the position of the pancreas
(in relation to stomach, duodenum and spleen; _____perittoneal, and quadrant)
Pancreas is
- posterior to the stomach
- between the duodenum and spleen
- Retroperitoneal
- upper quadrants
What is the vasculature of the pancreas?
Anastomosis of celiac and SMA branches (superior mesenteric a)
What is secreted by the pancreas?
- Digestive enzymes
- trypsin, chymotrypsin (protein)
- pancreatic amylase (carbs)
- pancreatic lipase (fats)
- Bicarbonate buffer
- neutralizes acidic chyme
- establishes alkaline pH for pancreatic digestive enzymes
Where does the pancreas drain into (vein)
Splenic vein
Head of the pancreas is associated with the _____ and the tail with the ______
Head of the pancreas is associated with the duodenum and the tail with the spleen
What are the endocrine secretions of the pancreas? Where are they released from?
Hormones:
- glucagon (from alpha cells)
- insulin (from beta cells)
- Somatostatin (from delta cells)
- Islets of langerhans - associated with vasculature
The connective tissue of the pancreas that is NOT islets of langerhans and that drains into ducts is called?
Pancreatic acini (acinus sing.)
What is the exocrine secretion from the pancreas?
From Pancreatic acini
- Water, ions and digestive enzymes
- buffers (sodium bicarbonate)
How does the pancreas prevent enzymes from eating through epithelium?
Centroacinar cells - secrete bicarbonate buffer and regulate pre-enzyme release from acinar cells
What type of cell makes up the ducts leading from the pancreas?
Centroacinar cells
What are the two types of cells of the pancreatic acinus?
- Acinar cells - secrete digestive enzymes (amylase, lipase, proteinase)
- Centroacinar cells - secrete buffer/regulate pre-enzyme release
The main pancreatic duct joins the bile duct and goes through the ______ and ______ (layer of duodenum) as the ______
The main pancreatic duct joins the bile duct and goes through the Circular and longitudinal smooth mm (layer of duodenum) as the hepatopancreatic ampulla
What is the largest gland in the body?
Liver
What is the vasculature of the liver?
Celiac trunk (hepatic artery) and hepatic portal vein
Is the liver intra or retroperitoneal?
Intraperitoneal
What are the three ways presented in lecture through which the liver regulates metabolism
- Carbohydrate, protein and fat metabolism
- Regulates circulating levels of all that is absorbed by the intestines
- Inactivates toxic compounds and metabolic waste absorbed from the intestine - so by the time it arrives at kidney it’s non-toxic
What are two ways in which the liver participates in haematological regulation?
- Destroys aged/damaged RBC’s, cellular debris and pathogens
- Secretes plasma proteins into blood (osmotic concentration, nutrient transport, clotting system)
What byproduct from the liver is required for digestion of lipids? What is it composed of?
Bile (water, ions, bilirubin, bile salts)
Found in the lesser omentum is the ____ through which everything enters the liver
Found in the lesser omentum is the Porter/Portal Triad through which everything enters the liver
All blood drainage from the intestines flows to the _____ before returning to the heart
All blood drainage from the intestines flows to the Liver before returning to the heart
In the liver, there is a mixing of _____ and ______ _______ blood
In the liver, there is a mixing of oxygenated and deoxygenated nutrient-rich blood
What type of molecule does not go to the liver, and is instead delivered directly to the general circulation via the lymphatic system?
Large lipids (fat)
Epithelium associated with liver is called ______ and forms liver ______
Epithelium associated with liver is called hepatocytes and forms liver lobules
Arterial and venous blood mix in the _____ of the liver
Arterial and venous blood mix in the sinusoid of the liver
Blood flows from the periphery of a liver lobule to its _____
Blood flows from the periphery of a liver lobule to its Central vein
Blood from the _____ and the ______ mix within the _____ of the liver
Blood from the hepatic portal vein and the hepatic artery proper mix within the sinusoids of the liver
From the central veins, blood flows to the right and left _____ and then to the ______
From the central veins, blood flows to the right and left hepatic veins and then to the inferior vena cava
Bile is synthesized by the _____ and secreted into the _______
Bile is synthesized by the hepatocytes and secreted into the bile canaliculi
Bile flows _____ to the periphery of the lobules. At the vertices of the lobules, the canaliculi flow into _______
Bile flows radially to the periphery of the lobules. At the vertices of the lobules, the canaliculi flow into small biliary ducts
Small biliary ducts merge to form larger ducts eventually emptying into the _______ to the _______
Small biliary ducts merge to form larger ducts eventually emptying into the right and left hepatic ducts to the common hepatic duct
Bile is stored in the ______ and released via the _____ and then the _____ to the duodenum
Bile is stored in the gallbladder and released via the cystic duct and then the bile duct to the duodenum
The exocrine function of the liver is associated with:
Tight juntions of epithelium
Form small channels called canaliculi where bile is secreted into
(liver)
The endocrine surface of the endothelium is associated with the highly fenestrated _____
The endocrine surface of the endothelium is associated with the highly fenestrated sinusoid
The neck of the gallbladder goes into the ____ duct
cystic duct
Which two ducts join to become the bile duct?
Cystic duct (from pancreas) and common hepatic duct (from liver)
What happens when the hepatopancreatic sphincter is closed?
Bile flows into the gallbladder via cystic duct
What happens when the hepatopancreatic duct is open?
Bile flows into the duodenum via bile duct
Presence of chyme in the duodenum induces the release of what hormone that relaxes the sphincter and contracts the gallbladder?
Cholecystokinin (CCK)
What does cholecystokinin (CCK) cause?
- Cholecystokinin stimulates
- the gallbladder to contract and release stored bile into the intestine
- Relaxation of the hepatopancreatic ampulla and opening of the hepatopancreatic sphincter
Which portion of the small intestine has most of the absorption?
Jejunum
Where is the jejunum located?
Intra or retroperitoneal?
Vasculature?
- Upper quadrants
- intraperitoneal
- Superior mesenteric artery and vein
The beginning of the jejunum is called the :
Duodenojejunal flexure
Compare the jejunum to the ileum
- jejunum has thicker walls, larger diameter and is more red than the ilium
- larger and greater number of plicae circulares (folds) than the ileum
What is the:
- Location
- intra or retroperitoneal
- vasculature
of the ILEUM
- lower quadrants
- intraperitoneal
- Sup Mesenteric A and vein
What is between the ileum and the cecum of the large intestine?
Ileocecal valve
What are the lymph nodules present in the ileum and what is their primary purpose?
Peyer’s patches
Protect from colonic bacteria
What are the four cells of the villar epithelium in the small intestine?
- microvilli
- main epithelial cell
- absorptive
- goblet cell
- mucin
- enteroendocrine cell
- regulator - release many hormones
- paneth cell
- immunity - determines gut flora
What happens to sugars in the digestive system (carbs)
Broken down into monosaccharides
Absorbed in Small intestine
Go into Hepatic Portal Circulation
Proteins are broken down into _______ and end up in ________ circulation
Proteins are broken down into amino acids and end up in hepatic portal circulation
What happens to fats in the digestive system?
Broken down into fatty acids and then into chylomicrons (fat and bile salt) absorbed into lacteals and go directly into the lymphatic system where it forms chyle which goes into the thoracic duct and to the heart
(NO Liver Filtration - fatty diet impacts heart)
What is absorbed in the large intestine?
- Water,
- electrolytes,
- vitamins produced by colonic bacteria (K and B12)
What quadrants would you find the large intestine?
All four
What parts of the large intestine are intraperitoneal and what parts are retroperitoneal?
Intra: Have a mesentery
- Cecum,
- Transverse
- Sigmoid
Retro: no mesentery - associated with post. body wall
- Descending
- For anchorage
- Ascending
- For anchorage
- Rectum
What is the vasculature of the large intestine?
- Superior mesenteric artery and vein
- until left colic flexure
- Inferior mesenteric artery and vein
- From left colic flexure (so descending colon onwards)
At rest, is the ileocecal valve open or closed?
Closed
What is the appendix important for?
Filled with lymphatics
Important for maintaining bacteria inside the colon
At what anatomical point does the ascending colon “turn”?
Right Colic Flexure
The transverse colon turns at the ________ and becomes the descending colon
The transverse colon turns at the Left Colic Flexure and becomes the descending colon
The “pouches” of the large intestine are called?
Haustra (Haustrum sing.)
Haustra is to the large intestine what _______ is to the small intestine.
Haustra is to the large intestine what plicae circulares (circular folds) is to the small intestine.
What is the function of the haustra?
Help with contraction => to keep things moving through the large intestine
What are teniae coli?
Longitudinal smooth muscle layer - helps keep things movin
What are 4 notable features of Colonic Epithelium as mentioned in the lecture
- Lacks villi
- Goblet cells - lots of mucous because we are absorbing water - mucous keeps things moving
- a few absorptive cells (for vitamins B12 and K)
- Lots of lymphatic nodules
What type of epithelium makes up the rectum?
Simple columnar epithelium
What is the function of the rectum?
Temporary storage for feces
What happens as the rectum fills?
Stimulates defecation - retroperitoneal = can feel when it is full
What type of epithelium makes up the anal canal?
Non-keratinized to keratinized stratified squamous epithelium
Smooth muscles (especially circular) associated with the rectum and large intestine thickens to become the _______ (sphincter)
Smooth muscles (especially circular) associated with the rectum and large intestine thickens to become the internal anal sphincter (sphincter)
What type of innervation does the internal anal sphincter have?
(Hint, think of how it is created)
Autonomic - because smooth muscle
Created from thickening of the smooth muscle associated with the rectum and large intestine
What nerves innervate the internal anal sphincter?
S2,3,4 (pelvic splanchnic nerves)
“S2,3,4 keeps the 3 p’s off the floor” (poop, pee, penis)
What division of the nervous system controls the external anal sphincter?
Somatic (voluntary control)
What forms the external anal sphincter?
Thickening of the pelvic floor [spec. the puborectalis muscle (one of the levator ani mm)] forms the 3 layers of the external anal sphincter
