The Digestive System

CCK (Cholecystokinin) Stimulus: Receptors: Effectors: Response:

1. Fat in intestine 2. SI enteroendrocrine cells 3. Gastric glands inhibited and empties 4. releases in pancreas and gall bladder (decreases hunger: CNS)

Gastrin Stimulus: Sensors: Effectors: Response:

1. Food sensation (senses and distention) 2. G cells in gastric pits 3. gastric secretary cells, gastric smooth muscles, pyloric sphincter (opens) 4. increases gastric activity and motility

GIP (Glucose-depended Insulinotropic Peptide) Stimulus: Sensors: Response:

1. Glucose (hyperosmolarity) 2. SI enteroendocrine cells 3. insulin secretion

alkaline tide

1. Hydrogen ions (H+) are generated inside a parietal cells as the enzyme carbonic anhydrase converts CO2 and H2O to carbonic acid (H2CO3), which then dissociates. 2. a counter transport mechanism ejects the bicarbonate ions into the interstitial fluid and imports chloride ions into the cell. 3. the chloride ions then diffuse across the cell and exit through open chloride channels into the lumen of the gastric glands. 4. the hydrogen ions are actively transported into the lumen of the gastric glands.

gastric glands

Fundus and body secrete most of the acid and enzymes involved in gastric digestion.

sucrase

Glucose + fructose

Neural Control Mechanism (long)

Long reflexes involving interneurons and motor neurons in the CNS provide a higher level of control over digestive and glandular activities, generally large scale peristalsis that moves materials from one region of the festive tract to another. long reflexes may invoke parasympathetic motor fivers.

parietal cells

Parietal cells Secrete: Intrinstic Factor (a glycoprotein that facilitate the absorption of Vitamin B12 across the intestinal linking. Also secretes hydrochloric acid (HCl)

What are the 3 pairs of the Salivary Glands? What are the composition of Saliva? What is the control center of the Salivary glands? (2) What is the Response of the stimuli?

Parotid, Sublingual, and Submandibular water (mostly, Buffers (pH 7.2), antibodies, amylase (breakdown of starch), Mucin, and Urea. Parasympathetic is stimulated: lots of watery saliva Sympathetic is inhibited: little, viscous saliva Smell, Taste or Thought of food

chief cells

Secrete pepsinogen, an inactive proenzyme. Acid (HCl) in the gastric lumen converts pepsinogen to pepsin, an active proteolytic (protein-digesting) enzyme.

Neural Control Mechanism (short)

Short reflexes are often triggered by chemoreceptors or stretch receptors in the walls of the digestive tract; the controlling neurons are located in the mytenteric plexus.

mucosa

The inner lining of the digestive tract is a mucous membrane consisting of an epithelium, which is moistened by glandular secretions, and lamina propria of areolar tissue.

gall bladder

the pear shaped reservoir for bile after it is secreted by the liver.

serosa

along most portions of the digestive tract within the peritoneal cavity, the muscularis externa is covered by a layer of visceral peritoneum. (not serosa covering in the oral cavity, pharynx, esophagus, and rectun.

enterokinase

an enzyme in the lumen of the small intestine that activates the proenzymes secreted by the pancreas.

amylase

an enzyme that breaks down polysaccharides; produced by the salivary glands and pancreas.

lactase

an enzyme that breaks down the milk sugar lactose glucose + galactose

G cells

are enteroendocrine cells that produce a variety of hormones.

maltase

glucose + glucose

pepsinogen

inactive protein enzyme but converts to pepsin by acid lumen

lacteal

lacteals transport materials that cannot enter blood capillaries.

pyloric sphincter

regulates the release of chyme into the duodenum

segmentation

rhythmic muscular contractions that mix material in digestive tract Bidirectional (back and forth movement)

villi

small mucosal projections that stick into the lumen of the small intestine. increase surface area for absorption.

muscularis externa

smooth muscles cells in 2 layers (circular layer and outer longitudinal layer). essential role is to move material along the digestive tract.

hydrolysis

the breakdown of chemical bonds through the addition of water molecules. the reverse is dehydration synthesis.

bile

the exocrine secretion of the liver; stored in the gallbladder and ejected into the duodenum.

peristalsis

waves of muscular contractions that propel material along digestive tract

pepsin

active enzyme (in low pH environment)

secretin Stimulus: Sensors: Response:

1. Acid chyme in intestine 2. SI enteroendrocrine cells 3. Gastric glands inhibited Gastric motility inhibited (pyloric sphincter) and gastric glands inhibited Pancreas buffer and bile production/secrection

VIP (Vasoactive Intestinal Peptide) Stimulus: Receptors: Response:

1. Local presence of food 2. SI enteroendocrine glands 3. intestinal glands (increase secretion) local pre capillary smooth muscles (vasodilation) glastic glands inhibited

Histology (4 layers)

1. Mucosa (muscous membrane and Lamina propria) 2. Submucosa 3. Muscularis externa (longitudinal and circular) 4. Serosa

Hormonal control Mechanism.

18 hormones that affect almost every aspect of digestive function, and some of them also affect the activities of other systems. these hormones are produced by enteroendrocrine cells.

What are the Functions of the Digestive System (5)

Ingestion Motility Digestion (big->small particles) Secretion Absorption

submucosa

a layer of dense irregular connective tissue that surrounds the mucosa