Digestive System

What is the main function of intracellular digestion in the digestive system?

The oxidation of glucose and fatty acids to make energy.

What is peristalsis?

Rhythmic contractions of the gut tube influenced by the parasympathetic and sympathetic nervous systems.

Describe the digestive pathway from mouth to anus.

Oral Cavity → Pharynx → Esophagus → Stomach → Small Intestine → Large Intestine → Rectum.

What initiates mechanical digestion in the oral cavity?

Mastication (chewing) of food.

What enzyme in the oral cavity hydrolyzes small sugars?

Salivary Amylase.

What role does lipase play in digestion?

It hydrolyzes fats.

What does the epiglottis do?

Prevents food from entering the larynx.

What parts make up the esophagus?

The top third is skeletal muscle and the bottom third is smooth muscle.

What are the roles of the gastric and pyloric glands in the stomach?

Gastric Glands- Found in Fundus

1. Mucous Cells: Secretes mucus

2. Chief Cells: Secrete pepsinogen

3. Parietal Cells: Intrinsic factor, and HCL which cleaves pepsinogen to pepsin

Pyloric Glands

1. G Cells: Secrete Gastrin and cause more HCL secretion by parietal cells and induce stomach mixing

What is chyme?

An acidic semifluid mixture resulting from digestion in the stomach.

How does CCK affect digestion?

CCK is released by small intestine in response to chyme entry and triggers the release of bile and pancreatic juice to be released

What is secretin?

A peptide hormone released upon chyme entry. Stimulates pancreatic enzyme release into duodenum, reduces HCL secretion, and stimulates bicarbonate secretion. Also acts as an enterogastrone (slows gut motility)

What is the primary function of the small intestine?

Chemical digestion and nutrient absorption.

What is the role of villi and microvilli in the small intestine?

Increase the surface area for absorption of nutrients.

What are the functions of the liver?

Produces bile

What does the gallbladder do?

Stores and concentrates bile.

How does fat absorption occur in the small intestine?

Short-chain fatty acids diffuse directly into capillaries; larger fats reform into triglycerides and enter lymphatics as chylomicrons.

Which vitamins are fat soluble?

Vitamins A, D, E, and K.

What major processes occur in the large intestine?

Primarily water absorption and feces concentration.

What is first part of small intestine?

The duodenum

What part of small intestine does absorption?

jejunum

What are the two types of sphincters at the anus?

Internal (involuntary/autonomic) and external (voluntary/somatic) sphincters.

What enzyme is secreted by the stomach that acts on proteins?

Pepsin, which is secreted by gastric glands in the stomach.

What are acinar cells?

cells of the pancreas that produce digestive enzymes and bicarbonate

What enzyme is produced in the pancreas that breaks down carbohydrates?

Pancreatic Amylase

What enzyme is secreted by the pancreas that digests proteins?

Trypsin, which is secreted by the pancreas.

What enzyme is secreted by the pancreas to help digest fats?

Pancreatic Lipase

What activates Salivary Amylase?

Activated by the presence of food in the mouth during chewing.

What activates Pepsin?

Activated from its precursor pepsinogen by the acidic environment (low pH) in the stomach.

What activates Pancreatic Amylase?

Activated by the presence of carbohydrates in the small intestine.

What activates Pancreatic Lipase?

Activated by the presence of fats in the small intestine and is assisted by bile salts.

What are the 4 pancreatic peptidases?

Trypsinogen, chymotrypsinogen and carboxypeptidase A and B

What activates the pancreatic peptidases?

enteropeptidase

Where does trypsin cleave?

Trypsin cleaves peptide bonds at the carboxyl side of lysine and arginine residues in proteins,

Where does chymotrypsin cleave?

peptide bonds at the carboxyl side of aromatic amino acids such as phenylalanine, tryptophan, and tyrosine.

Where does carboxypeptidase A and B cleave?

Carboxypeptidase A and B cleave peptide bonds at the carboxyl terminal end of proteins

Most digestive enzymes in intestines operate at what pH?

basic pH

What is bilirubin and how is it excreted?

Pigment in bile is bilirubin → a byproduct of breakdown of hemoglobin

Bilirubin travels to liver (where it is conjugated to a protein) and secreted into bile for excretion

If liver can’t process or excrete bilirubin, jaundice can occur

What two hormones are primarily responsible for hunger?

Glucagon and Ghrelin

What hormones is responsible for satiety?

Leptin and CCK