Chapter 41: Nutrition Flashcards
Alimentary canal
The complete digestive tract in more complex animals in contrast to the gastrovascular cavity in simpler organisms
Saliva
Complex mixture of materials:
- Mucus- lubricates food for easier swallowing
- Buffers- prevent tooth decay
- Antimicrobial agents- such as lysozyme
- Amylase- breaks down starch and glycogen
Gastric juice
Digestive fluid produced in gastric glands
Parietal cells- secrete H+ and Cl− separately into the lumen of the stomach
- Use an ATP-driven pump to secrete H+
- Cl− diffuse through specific membrane channels
Chief cells- secrete inactive pepsinogen which is activated to pepsin when mixed with HCl in the stomach
Mucous cells- secrete mucous whicih lubricates and protects the stomach lining
Carbohydrate digestion
Protein digestion
Nucleic acid digestion
Fat digestion
Fat digestion is facilitated by bile salts which act as emulsifiers to break apart fat and lipid globules
Oral cavity digestive enzymes
Stomach digestive enzymes
Pancreatic digestive enzymes
Intestinal epithelia digestive enzymes
Duodenum
Chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestin itself
Arrival of chyme triggers the release of the hormone secretin which stimulates the pancreas to secrete bicarbonate
Pancreatic enzymes trypsin and chymotrypsin are activate
Pancreatic secretions
Bicarbonate- serves to neutralize acidity of the stomach
**Proteases
Bile production
Bile is made in the liver and stored and concentrated in the gallbladder
Bile salts are a major component of bile that serve to facilitate fat digestion
Also function in the breakdown process of old erythrocytes
Intestinal cells
Large folds in the lining are studded with finger-like projections called villi
Within each villi each epithelial cell has many microscopic projections called microvilli that face the lumen; called the brush boarder
Blood capillaries perfuse each villi as well as a lacteal vessel
Intestinal absortion
Generally, NOT referring to fats
Most digestion occurs in the duodenum; the jejunum and ileum function mainly in absorption of nutrients
Transport across the epithelial cells can be passive or active depending on the nutrient
Capillaries drain into the inferior mesenteric vein and into the hepatic portal vein which carries nutrient-rich blood to the liver then to the heart
Intestinal fat digestion
Hydrolysis of fat by lipase in the duodenum generates fatty acids and monoglyceride
Epithelial cells absorb fatty acids and monoglycerides and recombine them into triglycerides
These fats are coated with phospholipids, cholesterol, and proteins to form water-soluble chylomicrons which are transported into the lacteal
Lymphatic vessels deliver chylomicron-containing lymph to large veins that return blood to the heart
Glucose homeostasis
Hormonal regulation of appetite
Cholesterol
Low-density lipoprotein (LDL) delivers cholesterol to cells for membrane production
High-density lipoprotein (HDL) scavenges excess cholesterol for return to the liver
Heart disease risk increases with a high LDL to HDL ratio
