Chapter 17 - Digestive System Flashcards

Vocabulary flashcards for Chapter 17 of Human Anatomy & Physiology covering the Digestive System.

Digestion

The mechanical and chemical breakdown of foods into forms that cell membranes can absorb.

Mechanical digestion

Breaks down large pieces of food into smaller ones but does not change chemical composition.

Chemical digestion

Uses enzymes to break down food particles, by changing them into simpler chemicals.

Alimentary canal

The food passageway, consisting of organs that extend from the mouth to the anus.

Accessory organs

Organs that empty secretions into the alimentary canal; food does not pass through them.

Mucosa

Innermost layer of the alimentary canal wall; mucous membrane that absorbs dietary nutrients and secretes mucus and enzymes.

Submucosa

Connective tissue layer of the alimentary canal wall that nourishes cells and transports absorbed food molecules.

Muscularis (externa)

Muscle tissue layer of the alimentary canal wall containing circular and longitudinal layers that move the tube and food materials.

Serosa

Outermost layer of the alimentary canal wall; serous fluid eliminates friction.

Mixing movements

Muscle in small sections contracts rhythmically, does not move materials in one direction. Example: segmentation in small intestine, churning in stomach.

Propelling movements / Peristalsis

Moves materials in one direction; ring of contraction progresses down the tube.

Parasympathetic impulses

Increase activities of the digestive system (secretion and motility).

Sympathetic impulses

Inhibit digestive actions (secretion and motility).

Submucosal plexus

Controls secretions in the alimentary canal.

Myenteric plexus

Controls gastrointestinal motility.

Enteroendocrine cells

Secrete hormones to regulate GI organs and processes; found in the stomach and small intestine.

Mastication

The process of chewing.

Oral vestibule

The space between the cheeks, lips, and teeth.

Saliva

Lubricates and binds food together into a bolus; contains salivary amylase to begin chemical digestion of carbohydrates.

Mucous cells

Secrete mucus in the salivary glands.

Serous cells

Secrete watery substance containing salivary amylase in the salivary glands.

Parotid glands

Largest salivary glands found anterior and slightly inferior to the ears.

Submandibular glands

Salivary glands in the floor of the mouth on the inside surface of the mandible.

Sublingual glands

Small salivary glands located on the floor of the mouth inferior to the tongue.

Pharynx

Passageway for food and air, extending from the nasal cavity to the esophagus.

Nasopharynx

Superior to the soft palate; passageway for air only and connected to the middle ear through the auditory (eustachian) tube.

Oropharynx

Posterior to the mouth down to the epiglottis; passageway for food and air.

Laryngopharynx

Inferior to the oropharynx from the epiglottis to the cricoid cartilage; passageway for food and air.

Esophagus

Connects the pharynx to the stomach and does not assist in digestion.

Hiatal hernia

When part of the stomach protrudes through the esophageal hiatus and into the thoracic cavity.

Lower esophageal sphincter (cardiac sphincter)

Relaxes to allow the passage of food and fluid into the stomach.

Stomach

J-shaped, pouchlike organ that hangs inferior to the diaphragm, in the upper-left portion of the abdominal cavity.

Rugae

Thick gastric folds in the inner lining of the stomach that unfold when the stomach distends.

Gastric pits

Located at the ends of tubular gastric glands in the stomach.

Mucous neck cells

Secrete mucus in the stomach.

Chief cells

Secrete pepsinogen and gastric lipase in the stomach.

Parietal cells

Secrete hydrochloric acid (HCl) and intrinsic factor in the stomach.

Enteroendocrine cells

Secrete hormones that regulate gastric secretion and/or motility in the stomach.

Cephalic phase

Increased parasympathetic activity (via Vagus nerve) due to sight, taste, smell, and thought of food.

Gastric phase

Stretch of the stomach wall increases gastrin secretion, which increases gastric secretions; HCl released from parietal cells comes from blood, leading to an alkaline tide in blood.

Intestinal phase

Initially releases intestinal gastrin, which increases gastric secretions; as the duodenum fills, a sympathetic reflex inhibits gastric release; enterogastric reflex ensures stomach slows down as duodenum fills.

Pancreas

An exocrine gland that secretes digestive fluid called pancreatic juice.

Pancreatic acinar cells

Make up most of pancreas, and release pancreatic juice into tiny ducts which lead to the pancreatic duct.

Pancreatic duct

Empties into the duodenum of the small intestine.

Hepatopancreatic sphincter (of Oddi)

Surrounds ampulla; controls movement of bile and pancreatic juice into duodenum.

Pancreatic amylase

Splits starch and glycogen into disaccharides.

Pancreatic lipase

Breaks down triglycerides.

Trypsin

Digests proteins; released as inactive trypsinogen, which is activated by enterokinase in the small intestine.

Chymotrypsin

Released as inactive, activated by trypsin; digest proteins.

Carboxypeptidase

Digests proteins; released as inactive, activated by trypsin.

Nucleases

Digest nucleic acids.

Bicarbonate ions

Make pancreatic juice alkaline; buffer stomach acid.

Secretin

Stimulates pancreas to release pancreatic juice high in bicarbonate ions.

CCK (cholecystokinin)

Stimulates pancreas to release pancreatic juice high in enzymes.

Liver

The largest internal organ, located in the upper right quadrant of the abdominal cavity, just inferior to the diaphragm.

Falciform ligament

Fold of visceral peritoneum that separates the right and left lobes of the liver and fastens the liver to the abdominal wall anteriorly.

Round ligament (ligamentum teres)

Fibrous remnant of the umbilical vein in the liver.

Quadrate lobe

Minor lobe of the liver near the gallbladder.

Caudate lobe

Minor lobe of the liver near the inferior vena cava.

Hepatic lobules

Functional units of the liver, containing hepatocytes around a central vein.

Hepatic sinusoids

Channels for blood between plates of cells in the liver.

Hepatic portal vein

Brings absorbed nutrients to sinusoids in the liver.

Hepatic artery

Brings oxygen-rich blood, which mixes with oxygen-poor blood from the portal vein, to the liver.

Kupffer cells

Macrophages found within the lobules of the liver.

Bile

A yellowish-green liquid that hepatic cells continuously secrete.

Bile salts

Produced from cholesterol; emulsify fats; the only bile component with a digestive function.

Bile pigments

Bilirubin and biliverdin, derived from hemoglobin breakdown.

Jaundice

Yellowing of skin, eye sclerae, and mucous membranes caused by blockage of bile ducts, diseases, or rapid red blood cell destruction.

Gallbladder

Pear-shaped sac found on the inferior surface of the liver that stores and concentrates bile.

CCK (cholecystokinin)

Stimulates the gallbladder to contract and release bile.

Gallstones

Small crystals formed from precipitated cholesterol in the gallbladder.

Small Intestine

Connects the stomach to the large intestine and receives secretions from the pancreas and liver.

Duodenum

Is ~25 cm long, and is the shortest, most fixed portion of the small intestine; receives acidic chyme from stomach, and secretions from pancreas and liver.

Jejunum

Mid-region of the small intestine.

Ileum

Near large intestine; the distal end narrows to form the ileocecal valve (sphincter muscle between the small and large intestine).

Mesentery

Folds in the peritoneum that attach the jejunum and ilium to the posterior abdominal wall.

Intestinal villi

Project into the lumen of the small intestine, increasing surface area; composed of simple columnar epithelium with microvilli, and connective tissue with many blood & lymphatic vessels (lacteals).

Plicae circulares

Submucosal folds in the small intestine that also further increase surface area.

Enterokinase

Converts trypsinogen from the pancreas into trypsin.

Peptidases

Break down peptides into amino acids.

Sucrase, maltase, lactase

Break down disaccharides into monosaccharides.

Lipase

Break down fat into fatty acids and glycerol.

Micelles

Loose complexes of fatty acids and bile salts, from which fatty acids can migrate to microvilli and be absorbed.

Chylomicrons

New triglyceride clusters encased in protein.

Small intestine

Has villi and plicae circulares.

Large Intestine (colon)

So named because its diameter is greater than that of the small intestine; about 1.5 meters long.

Cecum

Nearest the ileum of the small intestine. The appendix is a blind pouch in this region.

Ascending colon

From the cecum to the liver (right). A part of the colon.

Transverse colon

Runs across the top of the abdomen. A part of the colon.

Descending colon

From the spleen downward (left). A part of the colon.

Sigmoid colon

S-shaped portion that becomes the rectum. A part of the colon.

Rectum

Distal region of the colon.

Anal canal

Narrowing of the rectum that opens to the outside.

Taeniae coli

Longitudinal muscle is organized into 3 bands taeniae coli, that run down entire length of colon.

Haustra

Muscle bands create pouches called __, which help form feces.

Epiploic appendages

Small collections of fat in the serosa on the outer surface of the large intestine.

Mass movements

Peristaltic waves, 2 to 3 times/day, which usually follow meals.