PHYSIO: Chapter 5

ELECTRICAL PROPERTIES

• consist of spontaneously undulating waves of partial depolarization that sweep over the gut smooth muscle

MASTICATION (CHEWING)

Involves actions of jaws, tongue and cheeks

MASTICATION (CHEWING)

First act of digestion

DEGLUTITION/SWALLOWING

Voluntary and Involuntary stages

VOLUNTARY STAGES

• Food is molded into bolus by tongue and pushed back to pharynx

INVOLUNTARY STAGES

When food enters the pharynx, sensory nerve endings detect its presence and initiate the involuntary portion of the swallow reflex.

PHARYNX

Common opening of both respiratory and digestive tract

MYENTERIC PLEXUS

exist throughout the entire length of the esophagus

PERISTALSIS

Propulsive movement includes propelling of food through the esophagus

Rate of delivery, Consistency of delivery

2 IMPORTANT ASPECTS OF STOMACH FUNCTIONS

Proximal Region

Food storage area

Distal Region

• Known as untrum

• Intense slow activity and muscular contractions are frequently present

ADAPTIVE RELAXATION

major muscular reflex in proximal region

 distal stomach

 grinds and sifts food entering the small intents

VAGUS NERVE

Receive stimuli in the duodenum

Secretion of saliva

moisture and lubrication.

Cephalic Phase, Gastric Phase, Intestinal Phase

3 PHASES OF DIGESTION

Ivan Pavlov

Russian physiologist

Ivan Pavlov’s cephalic Phase

 an example of demonstration of a brain-gut interaction in Cephalic Phase.

Mastication, Prehension, Swallowing, Salivation

PRIMARY FUNCTIONS OF SALIVA:

Bolus

• well-lubricated mass.

Salivary amylase

this is a starch digesting enzyme. Present in: omnivores.

Lingual lipase

 this is a fat-digesting enzyme. Present in: young animals

Acini

The secretion of saliva came from the gland

Acini

• cells that secrete a fluid

Acinus

• small saclike cavity in a gland

Parotid glands

located under the ear and behind the mandible.

Parotid Glands

Secretes: watery or serous saliva,

Mandibular Glands

located in the intramandibular space.

Mandibular Glands

Secretes: serous and mucous saliva.

Lingual glands

located in the base of the tongue.

Lingual Gland

Secretes: Mucous saliva.

PNS

Salivary activity is regulated by the

Sympathetic nerve stimulation

 activates salivary secretory cells that also contain Beta-adrenergic receptors

Glandular

divided into three regions: cardiac mucosa, parietal mucosa, and pyloric mucosa.

Nonglandular

place for small amounts of fermentative (rumenlike) to be processed.

Glandular, Non-glandular

Two General Types of Gastric Mucosa:

Pepsin

Secreted by Gastric Chief Cells in an Inactive Form and is Subsequently Activated in the Stomach Lumen

Pepsin

Main gastric enzyme

Pepsin

 Secreted by Gastric Chief Cells in an Inactive Form and 1s Subsequently Activated in the Stomach Lumen

Zymogens

name for inactive proenzymes activated in the lumen.

 Parietal Cells

 Stimulated to Secrete by the Action of Acetylcholine, Gastrin, and Histamine:

liver

secretory gland of the digestive system

Liver

It secretes bile which is important in fat digestion.

Acinar Gland

The liver is a

Canaliculi

The Liver Is an Acinar Gland with Small Acinar Lumina Known as

Canaliculi

ithin the plates of the cell and are spaces join to form channels and connect to the bile ductules.

Hepatocytes - Canaliculi - Bile Duct System

Bile secretion process

Canaliculi

may be an acini lined by hepatocytes and empties into the biliary duct system.

bile duct epithelium

capable of changing the composition of canalicular bile and is active metabolically