Physiology Exam 4 Study Guide

What is GERD

Gastroesophageal reflux disease. It happens when stomach acid flows back up into the esophagus and causes heartburn

The function of the digestive system

Transfers nutrients, water, and electrolytes (e.g., Na+,Cl-, K+) from ingested food into the extracellular fluid (body’s internal environment)

The main processes of the digestive system

1. Digestion

2. Motility

3. Secretion

4. Absorption

Digestion

Breaking down food into the smallest possible molecules that can cross the epithelial cells lining intestinal tract and enter the capillary blood or lymphatic capillaries

Mechanical digestion

breaking food into smaller pieces (ex. teeth chewing)

Chemical digestion:

breaking bonds in food (ex. Enzymes breaking bonds in food molecules)

Digestive Enzymes:

Amylase

Maltase

Sucrase

Lactase

Pepsin

Trypsin

Chymotrypsin

Carboxypeptidase

Lipase

Which enzymes speed up the digestion of carbohydrates

• Amylase: Breaks bonds in polysaccharides

• Maltase, Sucrase and Lactase: Breaks bonds in disaccharides

Which enzymes speed up the digestion of proteins

• Pepsin

• Trypsin

• Chymotrypsin

• Carboxypeptidase

What Enzyme breaks down triglycerides after they are are emulsified?

Lipase

Motility

movement of material along gastrointestinal tract

• Smooth muscle contractions act to break up food, mix food with enzymes, and transport digested food through gastrointestinal tract

How motility is controlled

• Enteric nervous system: stretch from food increases motility and secretion

• Autonomic nervous system: increased parasympathetic nervous system activity increases motility, secretion, absorption and enzyme production

Gastrointestinal hormones:

How the digestive system knows which enzymes to secrete and whether to start motility

Food molecules bind to chemoreceptors throughout the GI tract

Circular muscles

Muscles contract just behind the bolus (food mass), pushes the bolus forward

• Mostly in esophagus

Segmental contraction

Segments of circular muscle contract alternatively

• Churns and mixes food

• Mostly in small intestine

Secretion:

Production of juices that are added throughout the digestive system

Absorption:

Movement of digested nutrients, water, vitamins, minerals and electrolytes from the lumen, through epithelial cells, and into capillary blood and lymphatic vessels

• Occurs mainly in small intestine

Why does the digestive tract have so many folds?

Folds increase surface area and allow more opportunities for absorption

What is the main site of absorption of water and nutrients

The small intestine in the main site of absorption to the villi

Digestion is divided into three phases:

1. the cephalic phase

2. the gastric phase

3. the intestinal phase

Where is the swallowing center?

Medulla Oblongata

After the epiglottis closes off the airway what is the sphincter that opens up to allow the bolus to enter esophagus

esophageal sphincter

Main functions of stomach

• Storage

• Digestion: mechanical and chemical digestion

• Immune Protection:

The Stomach is NOT a main site of absorption

Unique structures of the stomach

• Esophageal sphincter

• Pyloric sphincter

• Third layer of the muscularis: oblique layer

• Gastric pits: inside the pits are gastric glands