Digestive system

chapter 22

What are the four main regions of the large intestine?

The cecum, colon, rectum, and anal canal.

What is the primary function of the "normal flora" (bacteria) in the large intestine?

They synthesize certain vitamins (like Vitamin K), metabolize undigested materials, and prevent the growth of harmful bacteria

What triggers the defecation reflex?

The movement of fecal material into the rectum, which stretches the rectal wall

What are the two main types of secretions from the pancreas?

Endocrine (hormones like insulin/glucagon) and Exocrine (pancreatic juice containing digestive enzymes and bicarbonate ions).

What is the liver’s primary digestive function?

The production of bile, which is required for the digestion and absorption of lipids.

What are the main components of bile?

Water, bile salts, bile pigments (bilirubin), phospholipids, and cholesterol.

What is the function of the gallbladder?

It stores bile, concentrates it by removing water, and releases it into the duodenum when stimulated by the hormone cholecystokinin (CCK).

Where does carbohydrate digestion begin, and which enzyme is responsible?

It begins in the mouth with salivary amylase.

How are lipids processed before they can be absorbed into the small intestine?

They are emulsified by bile salts to form micelles, then broken down by pancreatic lipase into free fatty acids and monoglycerides.

How do lipids enter the bloodstream after absorption?

They are packaged into chylomicrons in the enterocytes, exit via exocytosis into lacteals (lymphatic vessels), and eventually enter the blood.

What is the "brush border," and why is it important?

It consists of microvilli on the small intestine surface that contain enzymes (like lactase and sucrase) to finalize the breakdown of nutrients for absorption.

A patient presents with abdominal pain in the right upper quadrant, especially after eating fatty meals. Their stool has become a light "clay" color. What is a likely cause?

A blockage of the common bile duct (likely by a gallstone). This prevents bile from entering the duodenum to digest fats and stops the bile pigments (bilirubin) from coloring the stool brown.

Why would a drug that blocks ACH (acetylcholine) receptors in the peripheral nervous system affect digestion?

ACH is the primary neurotransmitter of the parasympathetic nervous system (the "rest and digest" system). Blocking it would inhibit salivation, stomach acid secretion, and the motility (movement) of the digestive tract.

If a patient has a large portion of their stomach surgically removed (gastrectomy), why might they develop Vitamin B12 deficiency (anemia)?

The stomach lining produces intrinsic factor, which is required for the absorption of Vitamin B12 in the small intestine. Without enough stomach tissue, B12 cannot be absorbed

A patient is suffering from prolonged vomiting. How would this affect the pH of their blood, and what is this condition called?

It would cause the blood pH to increase (become more alkaline) because the body is losing acidic gastric juice ($HCl$). This condition is known as metabolic alkalosis.

Why does a person with a "stomach flu" sometimes experience a "burning" sensation in their nose or throat after vomiting?

The stomach produces Hydrochloric Acid (HCl) with a very low pH. When this acid refluxes or is vomited, it can irritate and "burn" the sensitive mucosal linings of the esophagus and nasopharynx.

How would the removal of the small intestine's "brush border" enzymes affect carbohydrate digestion?

Digestion would stall at the disaccharide stage. Even if pancreatic amylase breaks starch into maltose, the body couldn't break maltose down into glucose for absorption without those specific enzymes (like maltase and lactase) on the microvilli.

If the common hepatic duct is blocked, but the cystic duct is clear, can bile still enter the duodenum?

No. The common hepatic duct carries bile from the liver. If it is blocked, no bile can reach the cystic duct or the common bile duct, regardless of whether the gallbladder is functioning.