Notes: Pharynx, Esophagus, and Stomach (pg 6)

Pharynx: a fibromuscular passageway that connects the nasal and oral cavities to the larynx and esophagus

Swallowing

• Food is pushed into the back of the mouth by the tongue

Swallowing

• Food is pushed into the back of the mouth by the tongue

• When food reaches the fauces, sensory receptors initiate swallowing reflex (involuntary)

Swallowing• Food is pushed into the pharynx by the tongue• When food reaches the fauces, sensory

receptors initiate swallowing reflex (involuntary)

• Uvula is elevated to prevent food from entering nasopharynx. Epiglottis drops down to prevent food from entering the larynx.

Swallowing• Food is pushed into the pharynx by the tongue• When food reaches the fauces, sensory

receptors initiate swallowing reflex (involuntary)

• Uvula is elevated to prevent food from entering nasopharynx. Epiglottis drops down to prevent food from entering the larynx.

• Peristaltic movements propel food from pharynx into the esophagus

Esophagus: collapsible muscular tube, about 25cm long, passageway between pharynx and stomach

Esophagus: collapsible muscular tube, about 25cm long, passageway between pharynx and stomach• Posterior to trachea

Esophagus: collapsible muscular tube, about 25cm long, passageway between pharynx and stomach• Posterior to trachea • Passes through an opening in diaphragm

called the esophageal hiatus

Esophagus: collapsible muscular tube, about 25cm long, passageway between pharynx and stomach• Posterior to trachea • Passes through an opening in diaphragm

called the esophageal hiatus• Upper and lower esophageal sphincters

control movement of food into and out of esophagus

Stomach Structure4 regions:

Stomach Structure4 regions:1. Cardiac - small region around the opening from

esophagus

Stomach Structure4 regions:1. Cardiac - small region around the opening from

esophagus2. Fundus- most superior. Expands to provide

temporary storage

Stomach Structure4 regions:1. Cardiac - small region around the opening from

esophagus2. Fundus- most superior. Expands to provide

temporary storage3. Body- main portion

Stomach Structure4 regions:1. Cardiac - small region around the opening from

esophagus2. Fundus- most superior. Expands to provide

temporary storage3. Body- main portion4. Pyloric- at exit of stomach

Stomach StructureWall- contains three layers of muscle:• Innermost (oblique), Middle (circular), Outer

(longitudinal)• Contains folds (rugae) that allow for expansion

Output (pg 7)

• Draw stomach structure

Gastric Secretions (pg 6)• Lining of stomach contains numerous tubular

gastric glands. Produce 2-3 liters of gastric juice per day

Gastric Secretions (pg 6)• Lining of stomach contains numerous tubular

gastric glands. Produce 2-3 liters of gastric juice per day

• Chyme = Food + Gastric juice

Gastric Secretions (pg 6)• Lining of stomach contains numerous tubular

gastric glands. Produce 2-3 liters of gastric juice per day

• Chyme = Food + Gastric juice• 4 Types of Cells in gastric glands

1. Mucous Cells: Produce thick alkaline mucus to protect stomach lining and thin watery mucus to mix with food

Gastric Secretions (pg 6)• Lining of stomach contains numerous tubular

gastric glands. Produce 2-3 liters of gastric juice per day

• Chyme = Food + Gastric juice• 4 Types of Cells in gastric glands

1. Mucous Cells: Produce thick alkaline mucus to protect stomach lining and thin watery mucus to mix with food

2. Parietal Cells: Produce Hydrochloric acid (kills bacteria) and Intrinsic factor (for absorption of Vitamin B12)

Gastric Secretions (pg 6)• 4 Types of Cells in gastric glands

1. Mucous Cells: Produce thick alkaline mucus to protect stomach lining and thin watery mucus to mix with food

2. Parietal Cells: Produce Hydrochloric acid (kills bacteria) and Intrinsic factor (for absorption of Vitamin B12)

3. Chief Cells: Produce enzyme pepsin for protein digestion

Gastric Secretions (pg 6)• 4 Types of Cells in gastric glands

1. Mucous Cells: Produce thick alkaline mucus to protect stomach lining and thin watery mucus to mix with food

2. Parietal Cells: Produce Hydrochloric acid (kills bacteria) and Intrinsic factor (for absorption of Vitamin B12)

3. Chief Cells: Produce enzyme pepsin for protein digestion

4. Endocrine Cells: Produce gastrin (stimulates gastric gland secretion)

Regulation of Gastric Secretions

1. Cephalic phase: Begins when you see, smell, taste, or think about food. Medulla oblongata sends signal to stomach to increase secretion of gastric juice and the hormone gastrin. Prepares stomach to receive food.

Regulation of Gastric Secretions

1. Cephalic phase: Begins when you see, smell, taste, or think about food. Medulla oblongata sends signal to stomach to increase secretion of gastric juice and the hormone gastrin. Prepares stomach to receive food.

2. Gastric phase: Begins when food reaches stomach. Stretching of stomach wall stimulates more gastrin secretion, which leads to more production of hydrochloric acid and pepsin

Regulation of Gastric Secretions1. Cephalic phase: Begins when you see, smell, taste,

or think about food. Medulla oblongata, sends signal to stomach to increase secretion of gastric juice and the hormone gastrin. Prepares stomach to receive food.

2. Gastric phase: Begins when food reaches stomach. Stretching of stomach wall stimulates more gastrin secretion, which leads to more production of hydrochloric acid and pepsin

3. Intestinal phase: Begins when chyme passes from stomach into duodenum of small intestine. Decrease in pH in duodenum inhibits gastric secretion.

Stomach Emptying

• Pyloric sphincter opens and lets a small amount of chyme into small intestine. Then closes, pauses, and repeats

Stomach Emptying

• Pyloric sphincter opens and lets a small amount of chyme into small intestine. Then closes, pauses, and repeats

• Takes about 4 hours for stomach to empty after a meal, but time depends on the type of food eaten (carbohydrates faster, fat slower)

Sculpt

• Pharynx, esophagus, trachea, stomach (all three layers—show direction of muscle fibers in each)