Chapter 46: The Digestive System

Gastric Inhibitory Peptide

________ (GIP)- stimulated by chyme with high fat content.

Leptin

________- thought to be the main signaling molecule in the afferent portion of the control circuit for energy sensing.

Essential nutrients

________ are those that the body can not manufacture (vitamins, essential amino acids, long-chain unsaturated fatty acids, trace elements)

Liver

largest internal organ, main exocrine secretion is bile, modifies chemicals to maintain homeostasis

Chyme

________- the mixture of partially digested food and gastric juice.

Pepsinogen

________- the inactive form of pepsin (which digests proteins)

Mouth

________- a chamber for ingestion and initial processing.

nematodes, vertebrates, and earthworms

have one-way digestive tracts.

Exertion

________ increases metabolic rate.

Peristalsis

________- series of involuntary wave-like muscle contractions which move food along the digestive tract.

Insulin and Glucagon

from the liver, help maintain blood glucose concentration

Gastric Juice

________- an acidic secretion of the tubular gastric glands of the mucosa.

kilocalories

measures intake of food energy (under neuroendocrine)

large intestine

or colon, eliminates waste material, small intestine empties into the cecum, no digestion, only about 4% of absorption, many bacteria (excess is released in feces)

small intestine

aprx 14ft long, duodenum, jejunum, ileum, epithelial wall is covered with villi, epithelial cell lining is covered with microvilli, absorbed nutrients move into the blood or lymph capillaries

Invertebrate digestive systems

________ are bags of tubes.

Secretin

stimulated by increased chyme acidity

CCK

stimulated by high fat content

Gastrin

proteins in the food stimulate its secretion in the stomach

Enterohormones

duodenal hormones secreted into the blood

Hormones

stimulate salivary and gastric responses to sight, smell, and consumption of food

Pancreas

also functions as an endocrine gland, has hormones to digest proteins (trypsin and chimotripsin), starch (pancreatic amylase), and fat (lipase)

Accessory Organs

secrete enzymes into the small intestine

Stomach Acid

sterilizes food, protein digestion, activating pepsin, activating intrinsic factor, stimulating deliver of bile and enzymes, closing the esophageal sphincter, opening the pyloric sphincter

Stomach

acidic breakdown of food, chyme leaves the stomach through the pyloric sphincter and into the small intesine

Intrinsic Factor

popypeptide needed for the intestinal absorption of b12

Tissues of the Digestive Tract

serosa, mucosa, submucosa, muscularis externa

BMR

basal metabolic rate, minimum rate of energy consumption under defined resting conditions