Lecture 23c. Digestive (nutrients absorption) 🥖🥩🥑

What is the function of an enteroendocrine cell?

releases gastrin, serotonin, and histamine

Where are enteroendocrine cells located?

basement membrane of the mucosa

What is the function of a mucus cell (also called goblet cell)?

secretes mucus

What is the function of mucus within the stomach mucosa?

protects the stomach lining from acid and enzymes

Where are mucus cells found?

surface of gastric pits/glands

What is the function of a parietal cell?

secretes HCl and intrinsic factor

What is the role of HCl in the digestive system?

kills bacteria and activates pepsinogen

What is the role of intrinsic factor?

vitamin B12 absorption in the small intestine

What is the function of a chief cell?

secretes pepsinogen

What happens to pepsinogen after secretion from chief cells?

activated my HCl into pepsin

What is the role of pepsin?

digests protein

What do amylases break down?

starches (polysaccharides) into smaller sugars

Where does salivary amylase act?

the mouth

Where does pancreatic amylase act?

small intestine lumen

What breaks down disaccharides at the brush border?

brush border enzymes

What does pancreatic lipase break down?

triglycerides into monoglycerides and free fatty acids

What is the function of bile?

emulsifies fats into micelles

Where do micelles form?

small intestine lumen

What happens to fatty acids and monoglycerides at the brush border?

diffuse into enterocytes

What forms inside enterocytes after lipid absorption?

chylomicrons

What is the function of pepsin?

breaks proteins into smaller peptides in stomach

What is the function of pancreatic proteases?

break peptides into smaller fragments in small intestine lumen

What is the function of brush border proteases?

break peptides into individual amino acids

How are amino acids absorbed?

sodium-coupled active transport

How are glucose and galactose absorbed?

sodium-coupled active transport

How is fructose absorbed?

facilitated diffusion

Where do sugars and amino acids go after absorption?

hepatic portal vein to liver

How are lipids absorbed?

micelles deliver contents to enterocytes

What happens to lipids inside enterocytes?

reassembled into triglycerides and packed into chylomicrons

Where do chylomicrons go after absorption?

lymphatic lacteals

What is the hepatic portal circulation in the scope of the digestive system?

blood flow from digestive organs to liver

What blood vessels bring blood to the liver?

portal vein and hepatic artery

What does the portal vein carry?

nutrient-rich, oxygen-poor blood from intestines

What does the hepatic artery carry?

oxygen-rich blood to liver tissue

Where does blood flow after passing through liver sinusoids?

central vein

What is the function of the liver in portal circulation?

processes nutrients, detoxifies toxins, removes bacteria

What triggers the defecation reflex?

stretch of the rectal wall

What happens to the internal anal sphincter during defecation reflex?

relaxes automatically (smooth muscle)

What happens to the external anal sphincter during defecation reflex?

must be voluntarily relaxed (skeletal muscle)

What type of movement forces feces into the rectum?

mass movements from the colon

What nervous system initiates the defecation reflex?

parasympathetic nervous system

What voluntary action helps defecation?

valsalva maneuver (closing glottis and pushing)