Test 2 - Colombo - GI Flashcards
Name the 4 layers of the gut tube from deep to superficial.
Mucosa
Submucosa
Muscularis
Serosa/Adventitia
Name the tissues in the mucosa.
Epithelium
Lamina propriety
Muscularis mucosa
Name the tissue that makes up the submucosa.
Dense irregular connective tissue.
Name the tissue that makes up the muscularis layer.
Smooth muscle.
Name the tissue that makes up the serosa/adventitia.
Connective tissue
What is the difference between serosa and adventitia?
When the adventitia is covered with mesothelium, it is called serosa.
What is mesothelium?
Simple squamous lining epithelium
Where is adventitia found?
Generally attaches one organ to another
The smooth muscle associated with the digestive tract will have 2 things. An outer _____________ layer and an inner _______________ layer.
Longitudinal
Circular
What are the 3 regions of the pharynx from superior to inferior?
Nasopharynx
Oropharynx
Laryngopharynx
There are 2 types of GI motility. Name them.
Peristalsis
Segmentation
Describe peristalsis
Adj segment of the tract alternately contract and relax, moving food along
Describe segmentation
Nonadj segments of the tract alternately contract and relax. This moves food forward then backward. Food mixing and slow food propulsion occurs.
Name the three layers of the pharynx from deep to superficial.
Mucosa
Muscularis externa
Adventitia
What makes up the mucosa of the pharynx?
Non-keratinized stratified squamous, lamina propria (loose CT) w/ longitudinal elastic fibers
*There is no muscularis mucosa/submucosa
What makes up the muscularis externa of the pharynx?
Both circular and longitudinal skeletal muscle
What makes up the adventitia of the pharynx?
Connective tissue
When swallowing, what does the tongue, soft palate, epiglottis, and trachealis m. do?
Tongue - blocks off oral cavity
Soft palate - presses against back of nasopharynx
Epiglottis - covers the trachea
Trachealis m. - allows partial collapse of the trachea
The esophagus has three distinct parts as it relates to muscle. Describe them.
Upper 1/3 is skeletal
Middle 1/3 is mixed skeletal and smooth
Lower 1/3 is all smooth
Where are the esophageal glands found in the esophagus? Hint: They can be in 2 places.
What do these glands do?
What does the esophagus look a lot alike? How do you tell the difference?
Submucosa
Lamina propria
They add secretions that aid in the passage of stuff down the tube.
Vagina. The vagina does not have esophageal glands.
What are the 4 layers of the esophagus from deep to superficial?
Mucosa
Submucosa
Muscularis externa
Adventitia
What type of muscle is the esophageal sphincter formed from?
What does this sphincter do?
What disease results when this sphincter malfunctions?
Smooth muscle layer of muscularis externa.
Opens to let food into stomach. Contracts to close and keep stomach acid in the stomach.
GERD (Gastro-Esophageal Reflux Disease)
At the junction of the esophagus and the stomach, the epithelium transitions from _____________ to ____________.
Stratified squamous
Simple columnar
When acidic fluid is added to the bolus of food and mixed, what is the mixture called?
Chyme
What breaks down lipids?
Lipase
What breaks down proteins?
Pepsin
Does absorption happen in the stomach?
No. It is mixing and breaking down food.
_______ _______ are indentations in the mucosa that lead to ________ _________.
Gastric pits
Gastric glands
At the cardia of the stomach, the pits are ________ than the glands.
Shorter
In what part(s) of the stomach are pits and glands about equal in length?
Body/fundus
In the pylorus, describe the pits and the glands.
Longer pits
Shorter glands
Where are the glands located in the cardia?
Lamina propria
What do the glands in the cardia secrete and what is the point of the secretion?
Mucus
Helps glide things down into the stomach
In the glands of the body/fundus, what 2 types of cells are present?
What do these cells secrete?
Chief and parietal cells
Chief cells: Enzymes like pepsin and lipase
Parietal cells: Gastric acid (HCl) and intrinsic factor. THESE CELLS DO NOT SECRETE ENZYMES.
Why is intrinsic factor important?
It helps the small intestine absorb B12.
Why is B12 important?
It aids in the production/myelin of RBCs. Without B12, pernicious anemia results.
The pylorus looks similar to the cardia, but how does it differ?
Much longer pits.
T/F - The glands in the pylorus share the same function to the glands in the cardia.
True. They secrete mucus.
The gastric pit leads on to the gastric gland. Name the structures from lumen to base of the gland.
Pit - Pit cells
Isthmus (where the pit cells stop and the parietal cells start) - Parietal cells, pre-: pit, parietal, and neck cells, mini-granule cells (These pre-x cells are crucial in regenerating the gland)
Neck - Neck cells
Base - Pre-zymogenic cells, zymogenic cells, and enteroendocrine cells
The mucus neck cells secrete what?
These neck cells are round with ___________ granules.
Mucus
Bicarb
Apical
What do parietal cells secrete?
What do these cells look like?
Gastric acid (HCl) Intrinsic factor
Fried egg
What do the chief cells secrete?
Pepsinogen (Which becomes pepsin when it reacts with HCl)
Gastric lipase
What do the D cells secrete?
Somatostatin - inhibits acid. They are active when a person is “full”
What do the G cells (enteroendocrine) secrete?
What are G cells inhibited by?
Gastrin - this stimulates acid production
Also, 4 other hormones on a future card.
They also release Gastrin Releasing Peptide (GRP) which tells the vagus n. to tell the parietal cells to release HCl.
What do the enterochromaffinlike cells secrete?
Histamine - Stims acid
Where are stem cells found in the stomach?
On the top of the gland in the isthmus b/t pits and glands
The small intestine can be broken up into 3 segments with specific functions. Name the sections and the functions.
Duodenum - Site of most chemical digestion. Bile from gall bladder, bicarb, digestive enzymes from pancreas and brunner’s glands secrete mucus.
Jejunum - absorbs things digested in the duodenum.
Ileum - Absorption of bile-lipid micelles. Peyer’s patches.
What 3 modifications has the small intestine made to increase absorptive area?
Plica circulares
Villi
Microvilli
What are villi and what do they do?
Finger-like projections (contain lamina propria, microvasculature, lymphatics that absorb fats. They are covered in simple columnar epithelium) that increase the absorptive area by 10x
What are microvilli and what do they do?
Individual cell membrane folds that increase absorptive area by 20x.
What are Peyer’s patches?
How do they “see” antigens in the lumen?
Lymphoid tissue packed with immune cells. These easily distinguish the ileum.
Epithelial cells (Microfold [M] cells) sit over the patches and endocytose material and show it to lymphocytes and dendritic cells (Mucosal Associated Lymphatic Tissue [MALT])
The epithelium of the small intestine is made of what?
Simple columnar w/ microvilli (brush border)
What cells are the most common in the small intestine?
What do they secrete?
Enterocytes - absorptive columnar cells
Disaccharidases and amino peptidases. These digest disaccharides and dipeptides into monosaccharides and amino acids
What do goblet cells produce?
Mucus
What do paneth cells secrete?
Antimicrobial molecules and regulate immune response
What do enteroendocrine cells secrete?
Local and systemic signals relating to digestion and transit.
What do bile acids do?
Emulsify lipids to micelles
What does gastric lipase do?
Digests lipids to produce glycerol, FA, and monoglycerides.
What happens to lipids when acted upon by bile salts and lipases?
Diffusion across the membrane into the cell and are synthesized into triglycerides by the SER>Go to RER and are packaged into chylomicrons>Pass thru the blood and go into lymph
*A key point is that because of their lymph circulation, fats end up in the tissues, bypassing the liver.
What is the significance of the absorption of sodium and amino acids?
They are pumped out of the lumen and this creates high sodium conc. in the intercellular space. Water follows and it eventually drains into the capillary blood.
Where are the requisite vessels for absorption of protein and carbohydrates located?
In the lamina propria at the core of each villus.
Osmotic diarrhea is generally the result of what?
Malabsorption
Intestinal crypts (Crypts of Lieberkuhn) contain what?
Paneth cells
What are paneth cells and what do they do?
Innate immune cells that regulate microenvironment.
They release lysozyme, phospholipids A, and defensins
What do intestinal enteroendocrine cells release and what does each secretion do?
Secretin - Stims HCO3 and H20 secretion and inhibits acid secretion by parietal cells
CCK - Signals immediate satiety to the brain. Stims pancreatic acinar cell secretion
GIP - Stims insulin secretion by beta cells in pancreas
Peptide YY - Signals LT satiety to brain
Submucosal features give intestinal motility. What does the muscularis mucosa do?
Produce local movements of villi and plica circulae in order to gently mix/expel contents in the intestinal crypts
*There is also a submucosal plexus of parasympathetic fibers that regulate contraction
Intestinal motility is also aided by the muscularis externa. Tell me what you know about this.
It is the primary source of intestinal motility. It has circular and longitudinal bands. There are also myenteric (Aaurbach’s) plexuses that are collections of symp., parasymp., and sensory nerve fibers that regulate GI function.
What are the functions of the LI?
ABSORB H20 and electrolytes
Secrete bicarb and mucus
Move feces towards expulsion
The mucosa of the colon lacks _________, is penetrated by __________ ___________ __________, and has ________ and ___________ cells.
Villi
Tubular intestinal glands
Goblet, absorptive (colonocytes)
Histologically, what are tubular intestinal glands?
Simple columnar embedded in lamina propria w/ lymphocytes
What do absorptive cells have?
Short microvilli. Passive H20 transport happens after active transport of sodium into the cell basally
Muscularis externa has what 2 typical layers?
Longitudinal and circular
Outer layer has 3 extra longitudinal bands called the taeniae coli - which contracts lengthwise to move things along (parasympathetic control) - segmental, peristaltic, or anti-peristaltic movements
Rectum is the transitional zone b/t the _________ of the GI tract and the ___________ ___________, which sort of wraps around and tucks in.
Mucosa
External skin
T/F - The external anal sphincter is skeletal muscle.
True.
What are plica circulares and what do they do?
Circular folds (consist of mucosa and submucosa) that are best seen in jejunum.
These increase absorptive surface area by 3x.
