Alimentary Canal Structure and Function

Alimentary Canal Structure and Function

• The alimentary canal is a tube extending from the mouth to the anus, with various dilated, folded, and puckered sections.
• Different regions of the canal have specific functions and outcomes of their activity.
• Many glands are associated with the canal, playing a vital role in digestion.

Salivary Glands

• Three pairs of salivary glands secrete saliva into the mouth.
• Saliva is a digestive juice containing salivary amylase, which begins carbohydrate digestion.
• Saliva also lubricates the mouth and aids in bolus formation.

Oesophagus

• The oesophagus, or gullet, transports the food bolus from the mouth to the stomach.
• It is primarily a transit region, with no enzyme secretion, although salivary amylase may continue its action.
• Peristalsis, muscular contractions, move the bolus down.
• An epiglottis covers the trachea opening to prevent aspiration during swallowing.

Stomach

• The stomach is the widest part of the alimentary canal, behind the ribcage, under the diaphragm.
• Food stays in the stomach up to three hours, with protein-containing meals remaining longer.
• Strong stomach walls churn the food, mixing with gastric juice.
• Gastric juice contains gastric protease and hydrochloric acid for protein digestion.
• Rennin, in babies, solidifies and digests milk protein.
• The stomach lining is protected from acid erosion by mucus produced by goblet cells.

Small Intestine (Duodenum and Ileum)

• The duodenum is the first part of the small intestine, receiving secretions from the liver and pancreas.
• It is primarily involved in digestion.
• The duodenum wall contains glands producing enzymes to further digest carbohydrates and lipids.
• The ileum, the remainder of the small intestine, is involved in absorption of fully digested food.
• Features like its length, folded interior, and villi lining maximize absorption of nutrients.
• Capillaries absorb absorbed nutrients, while the lacteal absorbs fat digestion products.

Large Intestine (Colon and Rectum)

• The colon joins the small intestine to the rectum.
• Its function is to absorb water from the undigested food matter, reducing it to a semi-solid form (faeces).
• Its longitudinal muscle layer forms bands and bulges, aiding in this process.
• The rectum stores faeces until elimination.
• The anus, a sphincter, controls the elimination of faeces.

Liver and Pancreas

• The liver produces bile, which aids in the emulsification (breaking down) of fats.
• Bile is stored in the gall bladder and released into the duodenum when needed.
• Bile contains no enzymes but crucial bile salts for fat digestion.
• The pancreas secretes pancreatic juice, containing enzymes to break down protein, carbohydrate, and fat into simpler molecules for easier absorption.

Enzymes

• Enzymes are biological catalysts that speed up chemical reactions without being altered.
• They are specific, meaning each enzyme works on a particular substrate (e.g., protease on proteins, amylase on starch).

Peristalsis

• Peristalsis are muscular contractions that move food through the alimentary canal.

Digestion, Absorption, Egestion

• Digestion is breaking down complex food molecules into simpler, absorbable molecules.
• Absorption is the uptake of these simpler molecules into the bloodstream.
• Egestion is the removal of undigested material from the body.

Major Products of Digestion and Roles

• Some of the products are nitrogenous (amino acids), important for building tissues, hormones, etc.
• Sugars (e.g., glucose) are released into the blood and used for energy; excess is stored as glycogen. (Liver)
• Glycerol and fatty acids are components of fats and are also used for energy.

Digestive System Disorders

• Ulcers: Localized inflammation in the stomach and duodenum lining.
• Hepatitis: Liver inflammation caused by viruses or chemicals.
• Coeliac disease: Autoimmune disease, triggered by gluten intolerance, leading to digestive issues and nutrient deficiencies.

Explore the intricate structure and essential functions of the alimentary canal in this quiz. Dive into the roles of the salivary glands, oesophagus, and stomach to understand how digestion begins and progresses through the human body.