lect 4 pt 2

Stomach pathogen protection

Hydrochloric acid kills most of the bacteria that are swallowed with food.

Non-digestive function of the stomach

Short-term food storage, allowing a meal to be held while it is gradually digested and released into the intestines.

4 Substances absorbed by the stomach

1. Water,

2. alcohol,

3. certain ions

4. and select drugs in limited amounts.

what are Gastric pits and what do they do?

Narrow pits in the stomach lining containing specialized cells involved in gastric secretion.

Gastrin

A hormone secreted by enteroendocrine cells that stimulates secretion in other stomach cells.

Trigger for gastrin release

The presence of food in the stomach.

Two major functions of the small intestine

Chemical digestion and nutrient absorption.

what is the Duodenum and what is its shape?

The first section of the small intestine, forming a large backward C or D shape around the pancreas.

Main site of chemical digestion

The duodenum.

Role of pancreatic bicarbonate in the duodenum

Neutralizes acidic chyme and hydrochloric acid arriving from the stomach.

how many Pancreatic digestive enzymes and where do they go/what do they do?

Approximately $20$ enzymes secreted into the duodenum to breakdown food molecules.

Pancreatic duct

The tube that delivers pancreatic enzymes and bicarbonate into the duodenum.

Digestive substance produced by the liver

Bile.

Bile duct

The structure through which bile is delivered into the duodenum.

Role of bile in pH regulation in the duodenum

An alkaline fluid that helps neutralize stomach hydrochloric acid in the duodenum.

Action of bile on lipids

Emulsifies fats, preventing small lipid droplets from coalescing. (growing together to form a single mass)

Emulsification

The process of surrounding smaller fat droplets to prevent them from recombining into larger globules.

Structural property of bile in fat emulsification

Amphipathic nature with a hydrophilic end interacting with water and a hydrophobic end interacting with fats.

Gallbladder

An organ that stores and concentrates excess bile.

Jejunum

The middle segment of the small intestine primarily responsible for absorbing digested nutrients.

Functions of the ileum

Completes nutrient absorption and provides immune defense.

Peyer's patches

Lymphoid nodules located in the ileum that contribute to immune protection.

Approximate length of the small intestine

$$20\text{ feet}$$

Circular folds (plicae circulares)

Large folds in the small intestine wall that slow chyme movement and increase absorption time.

Villi

Finger-like projections of the intestinal mucosal lining that increase surface area for absorption.

Microvilli

Short, hair-like projections of the cell membrane on columnar epithelial cells that increase surface area for nutrient absorption.

Four surface-area specializations of the small intestine

Overall length, circular folds, villi, and microvilli.

Major functions of the large intestine

• Absorbing bacterial byproducts

• reabsorbing water and electrolytes,

• compacting feces,

• and storing waste.

Haustra

Repeating pouch-like segments along the length of the large intestine.

Rectum

The terminal segment of the large intestine that triggers elimination signals to the brain and assists in waste expulsion.

amphipathic =

having both a hydrophilic part and a hydrophobic part.