Unit 5- digestive system

What is the primary function of the digestive system?

To break down food into nutrients that can be absorbed and used by the body.

What is the path of food through the GI tract?

Mouth
→ Pharynx
→ Esophagus
→ Stomach
→ Small intestine
→ Large intestine
→ Rectum
→ Anus

What are the accessory digestive organs?

Organs that assist digestion but food does not pass through them.

Example:

• Liver

• Gallbladder

• Pancreas

What are the four layers of the GI tract wall?

1. Mucosa

2. Submucosa

3. Muscularis externa

4. Serosa

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What is the function of the mucosa?

• Secretion

• Absorption

• Protection

What is the function of the submucosa?

Contains:

• Blood vessels

• Nerves

• Lymphatic vessels

Provides support.

What is the function of the muscularis externa?

Responsible for movement of food through the GI tract.

Includes:

• Circular muscle

• Longitudinal muscle

What is the function of the serosa?

Outer protective covering that reduces friction.

Where does digestion begin?

The mouth

What type of digestion begins in the mouth?

Mechanical digestion:

• Chewing

Chemical digestion:

• Salivary amylase begins carbohydrate digestion

What is the function of the soft palate?

Closes off the nasopharynx during swallowing.

What is the function of the uvula?

Prevents food and liquid from entering the nasal cavity during swallowing.

What are the three major salivary glands?

• Parotid

• Submandibular

• Sublingual

What are the functions of saliva?

• Moistens food

• Begins carbohydrate digestion

• Helps form a bolus

What enzyme in saliva begins carbohydrate digestion?

Salivary amylase

What is deglutition?

Swallowing

What is the function of the upper esophageal sphincter?

Controls movement of food from pharynx into esophagus.

What is the function of the lower esophageal sphincter?

Prevents stomach acid from moving back into the esophagus.

What happens when the lower esophageal sphincter does not function properly?

GERD (acid reflux/heartburn)

What is GERD?

Gastroesophageal reflux disease.

Stomach acid flows back into the esophagus.

What are risk factors for GERD?

• Obesity

• Smoking

• Pregnancy

• Large meals

• Lying down after eating

What are the functions of the stomach?

• Stores food

• Mixes food

• Begins protein digestion

What sphincter controls food entering the stomach?

Lower esophageal sphincter.

What sphincter controls food leaving the stomach?

Pyloric sphincter.

Is the stomach a major site of absorption?

No.

The stomach mainly digests and mixes food.

Exception:

• Some drugs

• Alcohol

What are gastric glands?

Structures in the stomach lining that release digestive secretions.

What do parietal cells secrete?

• Hydrochloric acid (HCl)

• Intrinsic factor

What are the functions of HCl?

• Activates pepsin

• Breaks down proteins

• Kills bacteria

• Creates acidic environment

What does intrinsic factor allow the body to absorb?

Vitamin B12.

What are the three sections of the small intestine?

• Duodenum

• Jejunum

• Ileum

What is the primary function of the small intestine?

The major site of:

• Digestion

• Nutrient absorption

What occurs in the duodenum?

Receives:

• Bile

• Pancreatic enzymes

Major site of chemical digestion.

What occurs in the jejunum?

Most nutrient absorption occurs here.

What occurs in the ileum?

Absorbs:

• Vitamin B12

• Bile salts

What are villi?

Finger-like projections that increase surface area for absorption.

What are microvilli?

Tiny projections on intestinal cells that further increase surface area.

What are lacteals?

Lymphatic vessels inside villi that absorb fats.

What is the hepatopancreatic sphincter?

Controls the release of bile and pancreatic juice into the duodenum.

What is gastrin?

A hormone that stimulates the stomach to produce acid.

What does CCK do?

• Stimulates gallbladder contraction

• Causes release of bile

• Stimulates pancreatic enzyme secretion

What organ produces bile?

The liver.

What organ stores bile?

The gallbladder.

What is the function of bile?

Emulsifies fats into smaller droplets to help digest them.

Does bile digest fat?

No.

It breaks fat into smaller pieces so enzymes can digest it.

What are gallstones?

Hardened deposits that can block bile ducts.

What organ produces pancreatic enzymes?

The pancreas.

Where do bile and pancreatic enzymes enter the digestive tract?

The duodenum.

What is the primary function of the colon?

Absorbs water.

What happens if too much water is absorbed in the colon?

Constipation

What happens if not enough water is absorbed?

Diarrhea

What are the regions of the colon?

• Ascending colon

• Transverse colon

• Descending colon

• Sigmoid colon

What is the appendix?

A small pouch attached to the large intestine containing lymphatic tissue.

What is appendicitis?

Inflammation of the appendix.

What is the role of the internal anal sphincter?

Controls feces involuntarily.

Smooth muscle.

What is the role of the external anal sphincter?

Controls defecation voluntarily.

Skeletal muscle.

Which anal sphincter is voluntary?

External anal sphincter.

Food does not pass through which digestive organs?

Accessory organs:

• Liver

• Gallbladder

• Pancreas

A patient has trouble absorbing fats. Which structure may be damaged?

Lacteals

A patient has acid reflux. Which structure is likely malfunctioning?

Lower esophageal sphincter.

A patient cannot absorb nutrients efficiently. Which structure increases absorption surface area?

Villi and microvilli.

A patient has gallstones blocking bile release. What digestion process is affected?

Fat digestion.

Which organ is responsible for the majority of nutrient absorption?

Small intestine.

Which organ is responsible for water absorption?

Large intestine (colon).