Digestive System

What is the purpose of the digestive system?

• breakdown of food and absorption of nutrients

• Absorption of nutrients

What are the Digestive processes

1. ingestion

2. peristalsis

3. Mechanical Breakdown

4. Digestion

5. Absorption

6. Defecation

Ingestion

Taking food into the mouth (eating)

Peristalsis

Movement of food through the alimentary canal (one way flow)

Mechanical Breakdown

Breaking down big pieces and making them smaller without altering their chemical form. Done by our teeth.

Digestion

Chemical breakdown of food via enzymes. Specific enzymes break down specific food.

Absorption

Transport of nutrients into blood stream

Defecation

Elimination of indigestible waste, this is anything we cannot absorb or something we took all the nutrients from.

Peritoneal Cavity

Potential space in the abdomen with fluid. between the visceral and parietal peritoneum.

Serous Membrane

Two layers, Parietal (first layer) which is the lining of the cavities and Visceral (inner layer) which covers the surface of organs (attaches to organs)

Retroperitoneal Structures

Organs and vessels located in the space behind the peritoneum abdomen. Includes: kidneys, aorta, Inferior vena cava, and blood vessels

Mesenteries

Serves to anchor alimentary canal to the body. Lesser omentum, Greater omentum, and Mesentary

Lesser Omentum

Connect between liver and stomach

Greater Omentum

Connects stomach and colon, covers small intestines (hanfs like a flap that you can pull up)

Mesentery

Connects intestines large and small to the posterior wall of our abdomen

Alimentary canal

Muscular tube connecting the mouth to the anus

Muscularis externa

Peristalsis and segmentation

Submucosa

Connective tissue, elastic and allows for organ to return to original shape.

Mucosa

Epithelium for absorption of nutrients (deepest layer)

Accessory digestive organs

Secondary organs, not part of alimentary canal, sit outside however they provide breakdown of food (chemical and mechanical).

Oral cavity

Where mechanical breakdown mostly occurs

Palate

Hard palate and Soft palate ( uvula, soft tissue)

Dentation

Mastication via teeth, teeth occlude to break down food

Tooth anatomy

1. enamel: hardest substance

2. Dentin: replaced throughout life (living tissue)

3. Pulp Cavity: Blood supply and innervation

4. Periodontal ligament: anchors tooth to bone

Tongue

Manipulation of food and creations of bolus

Salivary Glands

where digestion begins, produces saliva

1. Mostens mouth/food

2. Enzymes begin digestion

What are the three salivary glands?

• Parotid gland

• Sublingual glands

• Submandibular gland

Peristaltic wave

Contractions of smooth muscles from superior to inferior. Involuntary wave.

Stomach

Muscular bag of many functions. widest part of alimentary canal. Highly acidic. Made up of many enzymes to protect itself from autodigestion.

Why do we need multiple muscle layers in the stomach

muscles do mechanical breakdowns (contract and mix food). mixes with gastric enzymes for chemical breakdown.

Stomach Functions

storage of food usually last 4 hours, produce chyme, and digest proteins

Chyme

Paste resulting from churning food some absorption.

Stomach lining

• Surface epithelium: secrete acid buffering mucus

• Gastric pit: secretion of pepsin and HCL

Mucous Neck cells

Produce mucus, clear white/substance to cover inner lining of stomach

Gastric glands

Parietal cells and chief cells

Gastric Ulcer

damage to surface epithelium, HCL and pepsin released into the body. A hole in stomach, mucus lining gets damaged or thin, so HCL and pepsin start to autodigest

Gastroesophageal reflux

Due to weakened cardiac sphincter, HCL and pepsin enter the esophagus and get burning sensation.

Small Intestine

Connects to stomach with the large intestine, its purpose is to digest and absorb nutrients

Subdivisions of the small Intestines

• Duodenum

• jejunum

• ileum

Duodenum

First and shortest section, C-shaped. Receives chyme, bile, and enzymes. Final phase of digestion, Neutralizes stomach acid

Liver

Storage of glucose, bile (gallbladder), Vitamins. etc. Detoxifies poisons and drugs. makes blood proteins

A

Bare area

B

Coronary ligament

C

Falciform ligament

D

Ligamentum teres

E

Gallbladder

A

Central Vein

B

Portal triad

C

Lobule

Portal triad ( three things)

• Interlobular bile duct

• Interlobular duct

• Interlobular artery

A

Central vein

B

Hepatocyte

C

Sinusoid

D

portal triad