Animal Nutrition

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5

Rectum

Stomach

Gall- bladder

Esophagus

Salivary glands

Mouth

Slide 36

The Oral Cavity, Pharynx, and Esophagus

The first stage of digestion is mechanical and takes place in the oral cavity.

Salivary glands deliver saliva to lubricate food.

Teeth chew food into smaller particles. This is mechanical digestion that increases the surface area exposed to the enzyme: salivary amylase, initiating breakdown of glucose polymers = carbohydrate digestion.

Slide 37

The tongue shapes food into a bolus and provides help with swallowing.

The region we call our throat is the pharynx, a junction that opens to both the esophagus and the trachea (windpipe).

The trachea leads to the lungs.

Slide 38

The esophagus conducts food from the pharynx down to the stomach by peristalsis.

Swallowing causes the epiglottis to block entry to the trachea, and the bolus is guided by the larynx, the upper part of the respiratory tract.

Coughing occurs when the swallowing reflex fails and food or liquids reach the windpipe.

Slide 39

From mouth to stomach: the swallowing reflex and peristalsis

Larynx

Trachea

Epiglottis up

Pharynx

Tongue

Glottis

Esophagus

Esophageal sphincter contracted

Food

To stomach

To lungs

Slide 40

From mouth to stomach: the swallowing reflex and peristalsis

Larynx

Trachea

Epiglottis up

Pharynx

Tongue

Glottis

Esophagus

Esophageal sphincter contracted

Food

To stomach

To lungs

Epiglottis down

Esophageal sphincter relaxed

Glottis up and closed

Slide 41

From mouth to stomach: the swallowing reflex and peristalsis

Larynx

Trachea

Epiglottis up

Pharynx

Tongue

Glottis

Esophagus

Esophageal sphincter contracted

Food

To stomach

To lungs

Epiglottis down

Esophageal sphincter relaxed

Glottis up and closed

Esophageal sphincter contracted

Sphincter relaxed

Relaxed muscles

Contracted muscles

Relaxed muscles

Stomach

Glottis down and open

Slide 42

Chemical Digestion in the Stomach

The stomach stores food and secretes gastric juice, which converts a meal to acid chyme.

Gastric juice is made up of hydrochloric acid and the enzyme pepsin.

Parietal cells secrete hydrogen and chloride ions separately.