Metabolism and the Digestive System

These 80 Q&A flashcards systematically review anatomy, physiology, digestion, absorption, metabolism, and hormonal regulation of the digestive system, preparing you for comprehensive exam questions.

What structures make up the oral cavity?

Tongue, teeth, lips, hard palate, and soft palate.

Where are the three major salivary glands located and what do they do?

Sublingual (under tongue), submandibular (floor of mouth), parotid (cheek); they secrete saliva that starts carbohydrate digestion.

Which salivary enzyme initiates carbohydrate digestion?

Salivary amylase.

List four key functions of the tongue.

Facilitates ingestion, sensation (taste & touch), swallowing, and vocalization while aiding mechanical & chemical digestion.

To which bones is the tongue anchored?

Mandible, styloid processes of the temporal bones, and the hyoid bone.

Which papillae contain most taste buds and where are they concentrated?

Fungiform papillae; larger at the back, smaller toward the tip and sides of the tongue.

Which tongue papillae provide touch receptors for moving food?

Filiform papillae.

What do lingual glands secrete, and when is the enzyme activated?

Mucus and lingual lipase; lipase becomes active in the stomach.

What is the main mechanical role of teeth?

Tearing, grinding, and mechanically breaking down food.

How many deciduous versus permanent teeth does a person have?

20 deciduous (baby) teeth and 32 permanent (adult) teeth.

How many incisors, cuspids, premolars, and molars are found in the adult dentition?

8 incisors, 4 cuspids (canines), 8 premolars (bicuspids), and 12 molars.

Name the two main anatomical parts of a tooth.

Crown and root.

What tissue surrounds the pulp cavity of a tooth?

Dentin.

What covers dentin at the root and at the crown?

Cementum covers dentin at the root; enamel covers dentin at the crown.

List the three regions of the pharynx and one function for each.

Nasopharynx (breathing & speech), oropharynx (breathing & digestion), laryngopharynx (breathing & digestion).

Which muscles propel food from the pharynx into the esophagus?

Pharyngeal constrictor muscles (superior, middle, inferior).

State four functions of the esophagus.

Connects pharynx to stomach, secretes lubricating mucus, generates peristalsis, and prevents reflux.

Name the two esophageal sphincters and their roles.

Upper esophageal sphincter (controls entry of food), lower esophageal sphincter (prevents gastric reflux).

Define deglutition and list its three phases.

Swallowing; voluntary phase, pharyngeal phase, and esophageal phase.

What is peristalsis?

Involuntary wave-like muscle contractions that propel food through the digestive tract.

Give three major functions of the stomach.

Stores food, mixes it into chyme, secretes gastric juice (HCl, pepsinogen, intrinsic factor).

Name the four regions of the stomach.

Cardia, fundus, body, and pylorus.

What are rugae?

Large folds of mucosa and submucosa that appear when the stomach is empty.

List the four layers of the stomach wall from inner to outer.

Mucosa, submucosa, muscularis externa, serosa.

Which stomach cells secrete hydrochloric acid and intrinsic factor?

Parietal cells.

Which stomach cells release pepsinogen?

Chief cells.

Which stomach cells produce the protective alkaline mucus coating?

Surface mucous cells (and mucous neck cells for acidic mucus).

Which gastric cells release hormones into the lamina propria?

Enteroendocrine cells.

Where is gastrin produced and what does it stimulate?

In the pyloric antrum; it increases gastric gland secretion and motility, and promotes gastric emptying.

What is ghrelin’s origin and primary effect?

Fundus of the stomach; signals the hypothalamus to stimulate appetite during fasting.

How does histamine affect gastric secretion?

It stimulates parietal cells to release HCl.

Where is somatostatin produced and what is its effect on the stomach?

Stomach, pyloric antrum, and duodenum; it inhibits all gastric secretions and motility.

Describe mechanical digestion in the stomach.

Mixing waves churn food with gastric juice; stronger waves at the pylorus push 3 mL chyme at a time into the duodenum (gastric emptying).

Which substances begin protein digestion in the stomach?

HCl denatures proteins and converts pepsinogen to pepsin, which cleaves proteins.

What is intrinsic factor and why is it important?

A protein secreted by parietal cells that enables vitamin B-12 absorption in the small intestine.

List the three segments of the small intestine and their approximate lengths.

Duodenum (~25 cm), jejunum (~0.9 m), ileum (~1.8 m/6 ft).

What structure marks the entry of bile and pancreatic juice into the duodenum?

The hepatopancreatic ampulla opening at the major duodenal papilla.

What are circular folds and their purpose?

Deep ridges of mucosa and submucosa that slow chyme and increase absorption surface area.

How do villi aid absorption?

Vascularized projections that increase mucosal surface area and contain blood capillaries and a lacteal.

What is the role of a lacteal?

A lymphatic capillary in each villus that absorbs dietary lipids into the lymphatic system.

Which enzymes are located on intestinal microvilli?

Brush-border enzymes that complete carbohydrate and protein digestion (e.g., maltase, sucrase, peptidases).

What do intestinal (crypt) glands secrete?

Alkaline intestinal juice that aids absorption and protects mucosa.

What do duodenal (Brunner’s) glands secrete and why?

Bicarbonate-rich alkaline mucus to neutralize acidic chyme entering the duodenum.

Name the four major parts of the large intestine.

Cecum, colon, rectum, and anus.

Identify the two main flexures of the colon.

Right colic (hepatic) flexure and left colic (splenic) flexure.

What type of epithelium lines the large-intestine mucosa?

Simple columnar epithelium with absorptive enterocytes and numerous goblet cells.

State four primary functions of the large intestine.

Absorb water & salts, synthesize vitamins, form feces, propel & eliminate feces.

What are haustral contractions?

Slow segmenting movements every ~30 min that mix and absorb water from residues.

Describe mass movements of the colon.

Strong peristaltic waves 3–4 times daily that drive contents toward the rectum.

What initiates the defecation reflex?

Stretching of the rectal wall by feces entering the rectum.

Differentiate the internal and external anal sphincters.

Internal: smooth muscle, involuntary; External: skeletal muscle, voluntary.

What is the peritoneum and its two layers?

A serous membrane that reduces friction and secures abdominal organs; parietal peritoneum lines the abdominal wall, visceral peritoneum covers organs.

Name three major peritoneal folds/ligaments.

Greater omentum, lesser omentum, and the mesentery (of small/large intestines).

What is the exocrine portion of the pancreas called and what does it secrete?

Acinar tissue (acini); secretes pancreatic juice into ducts.

List the main components of pancreatic juice and their pH role.

Water, salts, digestive enzymes, and sodium bicarbonate; bicarbonate makes the juice alkaline to neutralize acidic chyme.

Which intestinal enzyme activates trypsinogen to trypsin?

Enteropeptidase (enterokinase).

Name four major pancreatic enzymes and their substrates.

Pancreatic amylase (starch), pancreatic lipase (emulsified fats), trypsin/chymotrypsin/elastase/carboxypeptidase (proteins), ribonuclease & deoxyribonuclease (nucleic acids).

Which two hormones released from the duodenum stimulate pancreatic secretion?

Secretin (bicarbonate-rich juice) and cholecystokinin/CCK (enzyme-rich juice).

Give three major overall functions of the liver.

Produce bile, metabolize nutrients/toxins, and store vitamins/minerals/glycogen.

List six main constituents of bile.

Bile salts/acids, cholesterol, phospholipids, neutral fats, bilirubin pigments, and electrolytes.

How does bile assist fat digestion?

Bile salts emulsify large lipid droplets into smaller micelles, increasing surface area for lipase.

What is bilirubin and where does it come from?

A bile pigment produced from heme breakdown of old red blood cells.

Differentiate glycogenesis and glycogenolysis.

Glycogenesis: conversion of excess glucose to glycogen for storage; Glycogenolysis: breakdown of glycogen to glucose when needed.

Which lipoproteins are synthesized by the liver?

High-density lipoproteins (HDL) and low-density lipoproteins (LDL).

Which liver cells act as macrophages in sinusoids?

Kupffer (reticuloendothelial) cells.

Name the three regions of the gallbladder.

Fundus, body, and neck (leading into the cystic duct).

Trace the biliary tree pathway from liver to duodenum.

Left/right hepatic ducts → common hepatic duct + cystic duct → common bile duct → (joins main pancreatic duct) → hepatopancreatic ampulla → duodenum.

Which hormone triggers gallbladder contraction and bile release?

Cholecystokinin (CCK).

Where does carbohydrate digestion begin?

In the mouth by salivary amylase.

How are glucose and galactose absorbed from the intestine?

Co-transport with sodium ions into enterocytes, then into capillary blood → hepatic portal vein.

Define gluconeogenesis.

Formation of glucose from non-carbohydrate precursors (glycerol, amino acids, lactate) in the liver/kidneys.

Name the primary enzyme pair responsible for protein digestion in the stomach.

Hydrochloric acid (denatures) and pepsin (cleaves proteins).

How are amino acids absorbed into the bloodstream?

Via sodium-dependent co-transport into enterocytes, then diffusion into capillary blood → hepatic portal vein.

What is transamination?

Transfer of an amine group from one amino acid to a keto acid to form a new amino acid.

What stimulates the release of CCK from the duodenum?

Presence of lipids and partially digested proteins in chyme.

What hormonal state dominates the absorptive period and what is its main fuel?

Insulin dominates; glucose from recently ingested food is the primary fuel.

Which hormone predominates during the postabsorptive (fasting) state?

Glucagon (plus epinephrine).

During prolonged starvation, what fuels most cells and what is spared for the brain?

Fatty acids → ketone bodies fuel most tissues; glucose is conserved for brain and red blood cells.

Which enteroendocrine cells secrete gastrin?

G cells in the stomach and duodenal mucosa.

Briefly describe the three phases of gastric secretion.

Cephalic: sight/smell/taste triggers vagal stimulation; Gastric: food stretches stomach, gastrin & neural reflexes boost secretion; Intestinal: initial excitatory gastrin release then inhibitory enterogastric reflex and hormones slow gastric activity.