Introduction to Nutrition

Definition of Nutrition

• Nutrition is the process through which organisms obtain food and energy necessary for growth, repair, and maintenance of the body.

Components of Nutrition

• Ingestion: Intake of food into the body.
• Digestion: Breakdown of large food molecules into smaller, soluble molecules for absorption.
• Absorption: Movement of nutrients from the small intestine into the bloodstream.
• Assimilation: Utilization of nutrients by cells for energy or growth.
• Egestion: Elimination of undigested matter from the body.

Organs of the Alimentary Canal

• Mouth
• Oesophagus
• Stomach
• Small intestine
• Large intestine
• Anus

Essential Digestive Organs

• Liver
• Gall bladder
• Pancreas

Digestion Overview

• Digestion involves breaking down large food molecules into smaller soluble molecules for absorption, occurring in two types:
  • Physical Digestion: Mechanical breakdown of food into smaller particles.
  • Chemical Digestion: Enzymatic breakdown of molecules into smaller absorbable units.

Peristalsis

• Rhythmic, wave-like muscle contractions in the alimentary canal that propel food forward.
• Circular muscles contract while longitudinal muscles relax, and vice versa to facilitate movement.

Mouth Processes

• Salivary glands secrete amylase to digest starch into maltose.
• Chewing reduces food size to increase surface area for enzyme action.
• Peristalsis occurs in the oesophagus to move food.

Stomach Processes

• Peristalsis in the stomach walls churns food and mixes it with gastric juices.
• Gastric juices contain hydrochloric acid (activates protease and kills pathogens), protease (digests proteins), and mucus (protects stomach lining).

Chyme

• Chyme is the partially digested, liquefied food that moves to the duodenum.

Small Intestine Processes

• Peristalsis moves chyme through the small intestine.
• Pancreas secretes pancreatic juice, containing amylase, protease, and lipase, into the duodenum.
• Gall bladder releases bile, which contains bile salts that emulsify fats but lacks digestive enzymes.
• Epithelial cells produce maltase, protease, and lipase.

Alkaline Nature of Digestive Fluids

• Alkaline fluids (pancreatic juice, intestinal enzymes, bile) neutralize chyme and create a suitable environment for enzyme activity.

Digestive Enzymes

• Carbohydrates: Amylase, maltase (digest starch into glucose).
• Proteins: Proteases (digest proteins into amino acids).
• Fats: Lipases (digest fats into fatty acids and glycerol).

Digestion Summary

• Carbohydrates: Starch → Maltose → Glucose.
• Proteins: Proteins → Polypeptides → Amino Acids.
• Fats: Fats → Fatty Acids & Glycerol.

Absorption

• Absorption is the process where digested nutrients enter body cells.
• Nutrients absorbed in the small intestine include simple sugars, amino acids, fatty acids, glycerol, water, and mineral salts.

Adaptations of the Small Intestine for Absorption

• Villi increase surface area for nutrient absorption.
• Epithelial cells are one cell thick for short diffusion distance.
• Blood capillaries in villi transport absorbed nutrients, maintaining a diffusion gradient.
• Lacteals transport absorbed fats.
• Mitochondria in epithelial cells provide energy for active transport.

Nutrient Absorption

• Glucose and amino acids are absorbed through diffusion and active transport.
• Fatty acids and glycerol diffuse into the epithelium and form fat globules entering lacteals.

Assimilation

• Assimilation converts absorbed nutrients into new cytoplasm and energy.

Hepatic Portal Vein

• Transports nutrients from the small intestine to the liver.

Glucose Assimilation

• Glucose is used for energy or stored as glycogen in the liver for later use.

Amino Acid Assimilation

• Amino acids are used for growth and repair; excess undergo deamination in the liver.

Fats in the Liver

• Fats build protoplasm when glucose is sufficient; if glucose is low, fats provide energy.
• Excess fats are stored in adipose tissues.

Liver Functions

• Produces bile, deaminates amino acids, regulates blood glucose, breaks down hormones, detoxifies substances.

Deamination

• Removal of amino groups from amino acids, converting them into urea.

Blood Glucose Regulation

• Pancreas releases insulin (converts excess glucose to glycogen) and glucagon (converts glycogen back to glucose).

Harmful Effects of Alcohol Consumption

• Digestive: Increases stomach acid, risk of ulcers, leads to liver cirrhosis.
• Nervous: Slows reactions, affects judgment, risks dementia and brain shrinkage.

This quiz explores the essential aspects of nutrition, including the processes involved like ingestion, digestion, absorption, and assimilation. Understanding these concepts is crucial for maintaining health and supporting growth. Test your knowledge on how organisms obtain and utilize food for energy.