CHapter 24 - Exam 3 Digestive System

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chemical digestion

a series of reactions that break down large carbohydrates, lipids, and protein molecules into smaller molecules that can be absorbed and used by body cells

mechanical digestion

consists of various movements that increases surface area of the food to allow a thorough mixing with the digestive enzymes

absorption

the movement of the end products of digestion through the gastrointestinal tract wall into the blood or lymph for circulation to cells

defecation

the elimination of indigestible and undigested materials from the gastrointestinal tract

what are the 2 main groups that the organs of digestion are divided into

gastrointestinal tract and accessory digestive organs

what are the organs of the digestive tract

mouth, pharynx, esophagus, stomach, small and large intestine

what are the accessory digestive organs

teeth, tongue, salivary glands, liver, gallbladder, and pancreas

peritoneum

the largest of the serous membrane of the body

parietal peritoneum

lines the wall of the abdominal cavity

visceral peritoneum

covers some of the organs

mesentery

a double layer of peritoneum that attaches to the back wall of the abdominal cavity and supports the small intestines

greater omentum

part of the peritoneum attached to the stomach and to the colon and covering the intestines

what makes up the mouth (oral cavity)

cheeks, hard and soft palates and tongue

tongue

forms the floor of the oral cavity and is composed of skeletal muscle covered with mucous membrane

salivary glands

these lie outside the mouth and secrete the major portion of saliva through ducts, which enter into the oral cavity

what are the 3 pairs of salivary glands

Parotid, submandibular, and sublingual glands

what are the 3 parts of the tooth

crown, root and neck

dentin

what are the teeth composed of?

cementum

bone-like substance that attaches the root of the tooth to the periodontal ligament

salivary amylase

Enzyme in saliva that breaks down starch

esophagus

muscular tube that lies posterior to the trachea. it connects the pharynx to the stomach

deglutition

the act of swallowing

peristalsis

the process of wave-like muscle contractions of the alimentary tract that moves food along

bolus

A term used to describe food after it has been chewed and mixed with saliva

stomach

j shaped enlargement of the GI tract which begins at the bottom of the esophagus and ends at the duodenum (first part of small intestine)

rugae

mucosal folds in the lining of the stomach that expands surface area

gastric glands

glands of the mucosa of the stomach that secrete HCl and hydrolytic enzymes (primarily pepsinogen, the inactive form of pepsin, a protein-digesting enzyme), which begins the enzymatic, or chemical breakdown of protein foods.

what are the 4 types of secreting cells that make up the gastric glands

chief cells, parietal cells, mucous cells and G cells

chief cells

cells that release an inactive enzyme, pepsinogen

pepsinogen

The inactive form of pepsin that is first secreted by specialized (chief) cells located in gastric pits of the stomach.

parietal cells

cells that secrete HCl, which aids in the conversion of pepsinogen to active pepsin

intrinsic factor

a substance produced by the mucosa of the stomach and intestines that is essential for the absorption of vitamin B12

mucous cells

cells that secret mucous

G cells

cells that secret stomach gastrin

gastrin

polypeptide hormone secreted by the mucous lining of the stomach. it allows for the secretion of HCl and pepsinogen, relaxes the pyloric sphincter and increases motility

mixing waves

Gentle, ripping, peristalic movements that pass over the stomach every 15 to 25 seconds; softens and mixes food with gastric secretions to form chyme

mechanical digestion

consists of peristalic movements called mixing waves

chemical digestion

consists of the conversion of protein into peptides by the action of the enzyme pepsin

chyme

a semiliquid mass of partially digested food that passes from the stomach through the pyloric sphincter into the duodenum

secretin

peptic hormone produced by the mucous lining of the small intestine. decrease gastric secretion and motility

CCK (cholecystokinin)

...

pancreas

accessory organ which functions as both and endocrine and exocrine organ

pancreatic juice

contains enzymes that digest starch, proteins, fats, and nucleotides

bicarbonate ions

converts the stomach acid contents to a slightly alkaline pH. also inhibits stomach pepsin activity and promotes the activity of the pancreatic enzymes

nervous and hormonal mechanisms

how are pancreatic secretions regulated

left and right lobes

how is the liver divided

what are the lobes of the liver made up of

hepatocytes, sinusoids, kupffer cells and a central vein

hepatic artery and hepactic portal vein

the liver receives a dual blood supply from what 2 things

hepatocytes

cells that secrete bile that is transported by a duct system to the gallbladder for concentration and temporary storage

bile

a substance produced by the liver that breaks up fat particles

gallbladder

sac that hangs from the lower front margin of the liver. it functions to store and concentrate the bile produced by the liver

what is the small intestine divided into

duodenum, jejunum, ileum

maltase

an enzyme that acts upon maltose and converts it into glucose

sucrase

breaks down sucrose

lactase

enzyme that breaks down lactose

peptidases

Enzymes that break down proteins into amino acids

nucleases

pancreatic juice enzymes that digest nucleic acids into nucleotides

name the subdivisions of the large intestine

cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum and anal canal

how long does chyme remain in the large intestine

3 to 10 hours

name the 6 functions of the digestive system

1. ingestion
2. mechanical processing
3. digestion
4. secretion
5. absorption
6. excretion

mesentery

double sheets of peritoneal membrane that suspend portions of digestive tract within peritoneal cavity by sheets of serous membrane

lesser omentum

stabilizes position of stomach

falciform ligament

helps stabilize positions of liver

dorsal mesentery

enlarges to form an enormous pouch, called the greater omentum

mesocolon

a mesentery associated with a portion of the large intestine

mucosa

inner lining of the digestive tract

enteroendocrine cells

cells that secrete hormones that coordinate activities of the digestive trace and accessory organs

muscularis mucosae

a narrow band of smooth muscle and elastic fibers on the outer portion of the mucosa, contraction of this move the mucosal folds and villi

mucosa

The layer of epithelial tissue that lines body cavities in contact with the outside environment (respiratory, digestive, urinary, and reproductive tracts).

submucosa

layer of dense, irregular connective tissue that surrounds the muscularis mucosae

submucosal plexus (plexus of meissner)

innervates the mucosa and submucosa

muscularis externa

consists of smooth muscle; responsible for segmentation and peristalsis

serosa

a thin membrane lining the closed cavities of the body except in oral cavity, pharynx, esophagus and rectum

vestibule

space between the cheeks or lips and the teeth

gingivae

ridges of oral mucosa

salivary glands

three pairs of exocrine glands in the mouth that secrete saliva; the parotid, submandibular (submaxillary), and sublingual glands

parotid salivary glands

produce a serous secretion containing large amounts of salivary amylase

sublingual salivary glands

on the floor of the mouth; secrete mucus

submandibular salivary gland

located along the floor of the mouth in the mandibular grooves;
secrete a mixture of buffers, mucins and salivary amylase

pulp cavity

part of the tooth that receives blood vessels and nerves through the root canal

deciduous teeth

primary teeth

deglutition

Swallowing

name the 3 phases of swallowing

buccal, pharyngeal, esophageal

regions of the stomach (4)

cardia, fundus, body, pylorus

where are the gastric glands located

fundus and body of stomach

parietal cells

cells that secrete intrinsic factor and HCl

chief cells

cells that secrete HCl and pepsinogen

pyloric glands

Glands located in the walls of the stomach, secreting the hormone gastrin in response to certain substances in food.

where does nutrient absorption occur?

small intestine

duodenum

the segment of the small intestine closest to the stomach

duodenum

part of the small intestine that receives chyme from the stomach and neutralizes acids

jejunum

middle section of the small intestine

jejunum

what part of the small intestine is the location of chemical digestion and nutrient absorption

ileum

the final segment of the small intestine

plicae curculares

transverse folds in the intestinal lining. Permanent features, do not disappear when intestine fills.

brush border enzymes

small intestine enzymes that include disaccharidases and dipeptidases

enteropeptidase

brush border enzyme that does not participate directly in digestion, but does activate trypsinogen

enteroendocrine cells

produce intestinal hormones such as gastrin, CCK, and secretin

duodenal glands

those in the submucosa of duodenum that secrete alkaline mucus to help neutralize acidic chyme

pancreatic alpha amylase

What pancreatic enzyme breaks down carbohydrates or starches?

pancreatic lipase

Enzyme in pancreatic juice that breaks down triglycerides (fats and oils), creating fatty acids and monoglycerides

what are the 3 structures of the portal area

branch of hepatic portal vein, branch of hepatic artery proper, small branch of bile duct

which organ secrete bile

liver

3 functions of the liver

metabolic regulation, hematological regulation, bile production

gallbladder

which organ stores and concentrates bile prior to excretion

name the 3 areas of the colon

cecum, colon, rectum

ascending colon

the part of the large intestine that ascends from the cecum to the transverse colon

transverse colon

the part of the large intestine that extends across the abdominal cavity and joins the ascending to the descending colon

descending colon

the part of the large intestine that descends from the transverse colon to the sigmoid colon

sigmoid colon

the s-shaped curve between the descending colon and the rectum

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