Digestion and Nutrition - Chapter 36

Digestion and Nutrition - Chapter 36

• Mammals exhibit diverse dentition reflecting their dietary habits.
• Omnivores have various teeth for processing both meat and vegetation.
• Herbivores often have incisors for clipping and premolars/molars for grinding.
• Carnivores possess pointed incisors and enlarged canines for shearing flesh.

Human Digestive Tract

• Humans have a tube-within-a-tube body plan.
• Digestion is an extracellular process.
• Digestive enzymes are secreted by the digestive tract or nearby glands.

Mouth

• Three major pairs of salivary glands exist.
• Saliva contains salivary amylase, initiating starch digestion.
• The tongue is composed of striated muscle.
• The tongue mixes chewed food with saliva forming a bolus.

Swallowing

• Digestive and respiratory passages converge in the pharynx.
• The soft palate closes off the nasopharynx.
• The epiglottis covers the trachea opening, preventing food entry.
• Food travels through the esophagus via peristalsis.

Stomach

• The stomach wall has folds that flatten as the stomach fills.
• Gastric pits lead to gastric glands, containing cells secreting HCl and pepsinogen.
• Pepsin is a hydrolytic enzyme digesting proteins into peptides.
• Chyme is the mixture of food and gastric juices.
• Chyme eventually leaves the stomach.

Small Intestine

• Chyme enters the duodenum, receiving secretions from liver and pancreas.
• The liver produces bile, stored in the gallbladder, containing bile salts aiding fat emulsification.
• The pancreas produces pancreatic enzymes (amylase, trypsin, lipase).
• Amylase digests starch, trypsin digests protein, and lipase digests fat.
• Intestinal enzymes complete peptide and sugar digestion.
• Villi and microvilli increase the absorptive surface area within the small intestine.

Accessory Organs

• The pancreas is an exocrine gland releasing pancreatic juices into the duodenum.
• The liver helps maintain blood glucose levels (0.1%) by storing excess glucose as glycogen.

Large Intestine

• The large intestine comprises the cecum, colon, rectum, and anal canal.
• It's wider but shorter than the small intestine.
• Water, salts, and some vitamins are absorbed.
• The cecum includes the appendix.
• The colon segments are ascending, transverse, descending, and sigmoid colon.
• The anal canal opens to the exterior via the anus.

Nutrition

• Vitamins are organic compounds essential for metabolic processes and unavailable to the body.
• Antioxidants like vitamins C, E, and A defend the body against free radicals formed by metabolism.
• Vitamin D is produced from cholesterol in skin cells via UV exposure and acts in calcium uptake/metabolism.
• Minerals like calcium (for healthy bones) and sodium (for blood pressure control are essential).

Ideal American Diet

• Based on a pyramid structure prioritizing vegetable and fruit intake.
• Smaller portions of bread, cereals, rice, and pasta are also recommended; moderate consumption of meat, poultry, fish, eggs, nuts, etc.
• Fats, oils, and sweets are used sparingly.
• Dietary recommendations include serving amounts to maintain wellness.

Summary of Digestion (Table)

• A table summarizing carbohydrate, protein, and lipid digestion throughout the digestive tract (mouth, stomach, small intestine).