DIGESTIVE SYSTEM

Digestion

Digestion

The breakdown of ingested food.

Absorption

The passage of nutrients into the blood.

Metabolism

The production of cellular energy (ATP).

Alimentary canal

A continuous coiled hollow tube in the digestive system.

Accessory digestive organs

Organs that assist in digestion but are not part of the alimentary canal.

Mouth (Oral Cavity) Anatomy

The anatomical structures of the mouth, including lips, cheeks, hard palate, soft palate, uvula, vestibule, oral cavity, and tongue.

Tonsils

Palatine tonsils and lingual tonsil, which are part of the oral cavity.

Pharynx Anatomy

The anatomical structures of the pharynx, including nasopharynx, oropharynx, and laryngopharynx.

Functions of the Pharynx

Serving as a passageway for air and food, and propelling food to the esophagus.

Esophagus

The tube that conducts food from the pharynx to the stomach through peristalsis.

Layers of the Alimentary Canal Organs

Mucosa, submucosa, muscularis externa, serosa, and visceral peritoneum.

cardiac region, fundus, body, and pylorus, rugae, and external regions.

The anatomical structures of the stomach, including its location ARE…

Functions of the Stomach

Acting as a storage tank for food, site of food breakdown, initiation of protein digestion, and delivering chyme to the small intestine.

Specialized Mucosa of the Stomach

Simple columnar epithelium, mucous neck cells, gastric glands, chief cells, parietal cells, and endocrine cells.

Small Intestine

The body's major digestive organ, consisting of the duodenum, jejunum, and ileum.

Chemical Digestion in the Small Intestine

Enzymes from intestinal cells and pancreas, and bile from the gall bladder.

Villi

Fingerlike structures in the small intestine that increase its surface area for absorption.

Absorption in the Small Intestine

Water, nutrients, and lipids are absorbed through active transport, diffusion, and specialized lymphatic capillaries called lacteals.

Large Intestine

The organ that absorbs water, eliminates indigestible food as feces, and does not participate in digestion.

Structures of the Large Intestine

Cecum, appendix, colon, and rectum.

Food Breakdown and Absorption in the Large Intestine

No digestive enzymes are produced, resident bacteria digest remaining nutrients, and water and vitamins are absorbed.

Accessory Digestive Organs

Salivary glands, teeth, pancreas, liver, and gall bladder.

Salivary Glands

Glands that produce saliva, including parotid glands, submandibular glands, and sublingual glands.

Teeth

Structures that masticate (chew) food, including deciduous teeth and permanent teeth.

Pancreas

The gland that produces digestive enzymes and alkaline fluid, and also has endocrine functions.

Liver

The largest gland in the body, involved in digestion, detoxification, hormone degradation, and metabolism.

Gall Bladder

The sac that stores bile produced by the liver.

Processes of the Digestive System

Ingestion, propulsion, digestion, absorption, and defecation.

Peristalsis

Alternating waves of contraction that move foods from one region of the digestive system to another.

Segmentation

Moving materials back and forth to aid in mixing.

Mechanical digestion

Mixing of food in the mouth by the tongue; Churning of food in the stomach; Segmentation in the small intestine.

Absorption

End products of digestion are absorbed in the blood or lymph; Food must enter mucosal cells and then into blood or lymph capillaries.

Defecation

Elimination of indigestible substances as feces.

Parasympathetic division

Controls most reflexes in digestive activity.

Chemical and mechanical receptors

Located in organ walls that trigger reflexes.

Stimuli involved in the control of digestive activity

Stretch of the organ; pH of the contents; Presence of breakdown products.

Reflexes of Digestive Activity

Activation or inhibition of glandular secretions; Smooth muscle activity.

Nutrient

Substance used by the body for growth, maintenance, and repair.

Categories of nutrients

Carbohydrates, lipids, proteins, vitamins, minerals, water.

Carbohydrates

Simple sugars, starches, fiber.

Lipids

Triglycerides, phospholipids, fatty acids.

Proteins

Amino acids.

Body energy balance

Energy intake = total energy output (heat + work + energy storage).

Energy intake

Liberated during food oxidation.

Energy output

Heat is usually about 60%; Storage energy is in the form of fat or glycogen.