Ch 17 & 18 Digestive System

Digestive System - “Food Journey”

Food goes through: Mouth → Throat → Esophagus → Stomach → S Intestine → L Intestine → OUT

Mechanical Digestion

Breaking Down Food Physically

Mechanical Digestion Examples

Chewing, Mixing, Churning

Chemical Digestion

Breakdown foods chemically

Chemical Digestion Examples

Saliva, Stomach Fluid, enzymes

Organs of Alimentary Canal (7)

Mouth, Pharynx, Esophagus, Stomach, Small Intestine, Large Intestine, Canal

Digestive System Accessory Glands (4)

Salivary Gland, Liver, Gall Bladder, Pancreas

The 4 Layers of Alimentary Canal (Inside → Outside) (M-S-M-S)

Mucosa, Submucosa, Muscularis Mucosa, Serosa

Mucosa (INNER LAYER) - Touching the food

Structure: EPI Lining, CT, Glands / Function: Protection, Secretion (enzymes, mucus) , Absorb (nutrients)

Submucosa (RIGHT UNDER MUCOSA)

Structure: Loose CT, Blood Vessels, Nerves, Lymph Vessels / Function: Supply nutrients, carries absorbed nutrients away, control glands

Muscularis Mucosa (MUSCLE LAYER) - Moves Foods

Structure: Inner Circular muscle, Outer Longitudinal muscle, 2 layers (3 in stomach) of smooth muscle

Function: Perstalsis (Pushes food forward), Mixing (Churning)

Serosa (OUTER LAYER) - Outside covering

Structure: Thin CT, Serous membrane

Function: Reduce friction, protects organs

THINK: “This is where digestion actually starts happening”

Mucosa

THINK: "Support + Delivery”

Submucosa

THINK: “This layer is the motion”

MUSCULARIS

THINK: “Slippery outer wrap so organs don’t rub painfully”

SEROSA

Two main actions of food movement through Alimentary canal

Peristalsis & Mixing

Wave like contraction which push food from esophagus to anus

Peristalsis

Stomach has 3 muscle layer for mixing

Mixing

General Effects on Alimentary Canal

Parasympathetic & Sympathetic

Increase activity and movement (Rest & Digest / Speeds Digestion)

Parasympathetic (House keeper)

Decrease activity and movement (Stress / Slows digestion)

Sympathetic

MOUTH: Parts

Epithelium, Tongue, Frenulum, Hyoid bone, Hard palate, Soft palate, Uvula

Function: Stratified squamous (protection), tough, many layers of cells

Epithelium

Strong muscle covered with taste buds.

Function: forms bolus, taste, moves food

Tougue

Frenulum: Small fold of tissue under tongue/ hold tongue down and stabilize movement

Hyoid: U-shaped bone in neck, supports tongue and helps swallowing & speech

Frenulum & Hyoid Bone

Front roof of mouth

Made of bone

Lets you chew and breathe at same time

Hard Palate (FRONT)

Back roof of mouth

Made of muscle (Not Bone)

Move when swallowing to block nose so doesn’t go up

Soft Palate (BACK)

Small “dangly” piece at back of throat

Hang from soft palate

Function: Keep food out of nose, help with speech sounds, triggers gag reflex (protects airways)

UVULA