A&P Lec Activities of Digestive System

What are the 5 stages of digestion (in order)?

1. Ingestion

2. Digestion

3. Absorption

4. Compaction

5. Defecation

What is ingestion?

Selective intake of food

What is digestion?

Mechanical and chemical breakdown of food into a form usable by the body

What is absorption?

Uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph

What is compaction?

Absorbing water and consolidating the indigestible residue into feces

What is defecation?

Elimination of feces

What are the 4 main actions in the GI tract?

• Motility

• Secretion

• Digestion

• Absorption

What do the teeth do?

Chewing and grinding

What do the stomach/intestines do?

Mixing/churning

Peristalsis?

Movement and pushing absorbable food against epithelium

What are hollow organs?

Used in relaxation for filling and contraction for emptying

What are sphincters?

Used for relaxation when the gate is open and contraction for when the gate is closed

What would happen when fluid absorption in the GI tract is prevented by an inflammatory process like cholera?

• Loss of blood pressure

• Dehydration

• Electrolyte imbalances

What is the anatomical definition for digestion?

To break a larger molecule down, usually into smaller, absorbable molecules

Why does the “upper pharyngoesophageal sphincter” close during an inhale?

If it did not close, then we would be inhaling air and letting it travel to our GI tract which would cause a buildup of gas in our stomach

What is the anatomical definition of absorption?

Transport molecules across the epithelium of the GI tract and move them into the capillaries of the circulatory system

Folding increases what for absoprtion?

Surface area

What are the four levels of folding in the small intestine?

• Circular folds

• Villi

• Microvilli

• Intestinal epithelial cells

What are circular folds?

• Large, permanent folds oft he mucosa and submucosa

• Slow down food movement and increase absorptive surface area

What is villi?

• Finger-like projections extending from the mucosal surface

• Contain blood capillaries and a lacteal for nutrient absorption

What is microvilli?

• Tiny projections on the apical surface of epithelial cells

• Form the brush border and greatly increase surface area

What are intestinal epithelial cells?

• The absorptive cells lining the villi

• Their membranes contain enzymes and transport proteins for digestion and absorption

What does the mucosa consist of?

• Stratified squamous epithelium

• Lamina propria

• Muscularis mucosae

What makes up the muscularis externa?

• Inner circular layer

• Outer longitudinal layer

What makes up the serosa layer?

• Areolar tissue

• Mesothelium

What kind of digestion system do some animals have?

Egestion where organisms discharge undigested or unabsorbed food material from their bodies through the area they ingested it in

How many number of teeth do babies have vs adult?

Babies: 20

Adult: 32

What are many types of motility?

• Chewing/grinding

• Mixing/churning

• Peristalsis

• Hollow organs

• Sphincters

What is dentin vs enamel?

Dentin: Hard yellowish tissue that makes up most of the tooth

Enamel: A noncellular secretion that cannot regenerate and covers crown and neck of tooth

________ and ______ are living tissue and can regenerate?

Cementum and dentin are living tissue and can regenerate

What is cementum?

A dental mineralized tissue that covers the root and supports the tooth in the alveolar socket

The GI tract is from what to what?

Mouth to anus

What is the pathway for salivary secretion?

• Pressure receptors and chemoreceptors in mouth detect food or other inputs like thinking about food

• Salivary center in medulla is triggered and sends reflex to autonomic nerves

• Autonomic nerves send signal to salivary glands to produce saliva

• Increase in salivary secretion