Chapter 3 Nutrition digestion

Passive diffusion

*The movement of substances into or out of cells *without the expenditure of energy *no involvement of transport proteins in the cell membrane. *Also called simple diffusion.

Gastrointestinal Tract (GI)

*connected series of organs and structures *used for digestion of food and absorption of nutrients *also called the alimentary canal or the digestive tract.

Enzymes

Chemically, it is the action of _______ that divide nutrients into compounds small enough for absorption.

Sphincters

Circular bands of muscle fibers that surround the entrance or exit of a hollow body structure (e.g., the stomach) *act as valves to control the flow of material.

Gustatory Cells:

Cluster in taste buds in mouth and throat, work as nerve fibers to send info to brain (Taste)

Concentration Gradients

Differences between the solute concentrations of two substances.

In order to nourish our bodies, we must first:

Digest, absorb, and transport food to tissues and cells

GI tract

Digestion and absorption of the nutrients in foods occur at various sites along the ______

_____ & ______ are absorbed from the large intestine. Remaining material, waste, is excreted as feces

Electrolytes and water

hydrolysis

a reaction that breaks apart a compound through the addition of water

GI tract processes are regulated by both the:

hormonal and nervous systems

The GI tract is made up of:

mouth, esophagus, stomach, small intestine, large intestine (colon), rectum, and anus.

elimination takes place in the:

rectum

most chemical digestion and nutrient absorption occur in the:

small intestine

chemosenses definition

The chemical sensing system in the body, including taste and smell

Muscosa

The innermost layer of a cavity. It is composed of epithelial cells and glands. The inner layer of the gastrointestinal tract, also called the intestinal wall.

Serosa

The intestines are covered in

liver

The largest glandular organ in the body, *it produces and secretes bile *detoxifies harmful substances *helps metabolize carbohydrates, lipids, proteins, and micronutrients.

active transport

The movement of substances into or out of cells against a concentration gradient. *requires energy (ATP) *involves carrier (transport) proteins in the cell membrane

Chyme

The muscular contractions of the GI tract continue to break food up and mix it with various secretions, while simultaneously moving THIS SAME mixture along the GI tract. THIS MIXTURE IS CALLED...

phagocytosis

The process by which cells engulf large particles and small microorganisms. *Receptors on the surface of cells bind these particles and organisms to bring them into large vesicles in the cytoplasm. * "eating cell"

pincocytosis

The process by which cells internalize fluids and macromolecules. *cell membrane invaginates and forms a pocket around the substance. *"Drinking cell"

Where in the GI tract does the majority of nutrient digestion and absorption take place?

The small intestine Much absorption takes place in the jejunum and duodenum

The contents of which organ has the lowest pH? Which organ produces an alkaline or basic solution to buffer this low pH?

The stomach has the lowest PH, as it secretes a buffer that lowers the PH level to aid in digestion

endocytosis

The uptake of material by a cell *indentation and pinching off of its membrane to form a vesicle that carries material into the cell.

Peristalsis

The wavelike, rhythmic muscular contractions of the GI tract that propel its contents down the tract. *Think of a slinky type motion.

Name three "assisting" organs that are not part of the GI tract but that are needed for proper digestion. What are their roles in digestion?

- liver, pancreas, gallbladder Roles: liver: produces and secretes bile, detoxifies harmful substances, and helps metabolize carbohydrates, lipids, proteins, and micro-nutrients. Pancreas: secretes enzymes that affect digestion and absorption -secretes insulin to regulate metabolism and end products of foods gallbladder: stores and concentrates bile, then squeezes it into the duodenum of the Sm Int.

Describe the path food follows as it travels through the digestive system. Summarize the muscular actions that take place along the way.

-food starts in the mouth with chewing, -swallowing takes place when food travels down the esophagus via peristalsis muscular contractions and the epiglottis contracts to prevent choking. -from the esophagus food then travels to the stomach which is sealed and opened with sphincters, -next food goes to the intestines (small to large) and moves with peristalsis -lastly, the rectum, also a sphincter contraction

6 STEPS of digestion and absorbtion

1. Ingestion—the receipt and softening of food 2. Transport of ingested food 3. Secretion of digestive enzymes, acid, mucus, and bile 4. Absorption of end products of digestion 5. Movement of undigested material 6. Elimination—the excretion of waste products

Segmentation:

A contraction of intestinal muscles to break down food into smaller pieces - breaking compounds into enzymes to allow for absorption

cholesystokinin

A hormone produced by cells in the small intestine that stimulates the release of digestive enzymes from the pancreas and bile from the gallbladder.

Chyme

A mass of partially digested food and digestive juices moving from the stomach into the duodenum.

facilitated diffusion

A process by which carrier (transport) proteins in the cell membrane transport substances into or out of cells down a concentration gradient.

Serosa

A smooth membrane composed of a mesothelial layer and connective tissue. *The intestines are covered in serosa.

emulsifiers

Agents that blend fatty and watery liquids by promoting the breakup of fat into small particles and stabilizing their suspension in aqueous solution.

Common Chemical Sense:

Alerts to sensations with both taste and smell, such as menthol, spicy peppers. Uses throat, nose, mouth, and eyes.

Bile

An alkaline, yellow-green fluid *produced in liver, stored in gallbladder. * consists of salts, acids, phospholipids, cholesterol, and bicarbonate. *emulsifies dietary fats, aiding fat digestion and absorption.

pancreas

An organ that secretes enzymes that affect the digestion and absorption of nutrients *releases hormones, such as insulin, that regulate metabolism as well as the disposition of the end products of food in the body.

What is gastroesophageal reflux disease?

GERD: A condition in which gastric contents move backward (reflux) into the esophagus, causing pain and tissue damage. increases the risk for esophageal cancer

dietary changes are important in the treatment of:

GI Didorders

List the four major hormones involved in regulating digestion and absorption. What are their roles?

Gastrin: from stomach. stims gastric secretions and motility Cholecystokinin: causes gall bladder to contract, and sphincter of Oddi (bile duct) to relax (release of digestive enzymes from the pancreas and bile from the gallbladder.) insulin: regulates metabolism and end products of bile GIP (gastro intestinal peptides) from walls of duodenum; lows the release of the stomach contents into the small intestine and stimulates release of insulin from the pancreas.

enzymes

Large proteins in the body that accelerate the rate of chemical production in the body *They are not altered in the process

Circular Muscle

Layers of smooth muscle that surround organs, including the stomach and the small intestine.

absorption

Movement of substances in or across tissues (the passage of nutrients and other substances into the walls of the gastrointestinal tract and then into the bloodstream)

Olfactory Cells:

Nerve cells found in small patches of the nose and connect to the brain (Smell)

The Chemosenses include:

Olfactory cells Gustatory cells Common chemical sense

gallbladder

Pear shaped sac -stores and concentrates bile from the liver

Segmentation

Periodic muscle contractions at intervals along the GI tract *alternate forward and backward movement of the contents *Breaks apart chunks of the food mass and mixing in digestive juices.

3x per minute

Peristaltic waves from the stomach muscles occur about:

Enzymes:

Proteins that catalyze (speed up) chemical reactions, but don't change in the process

enterohepatic circulation

Recycling of certain compounds between the small intestine and the liver. -For example, bile acids move from the liver to the gallbladder, and then into the small intestine, where they are absorbed into the portal vein and transported back to the liver

Cephalic phase responses

Responses of the PNS to the sight, smell, thought, and sound of food. Also called preabsorptive phase responses.

Secretions from the stomach ________ the pH of stomach contents and begin the digestion of _______

Secretions from the stomach LOWER the pH of stomach contents and begin the digestion of PROTEINS

Chemosenses

Taste and smell belong to the:

Digestion

The breaking apart of food into smaller units

Lumen

cavity or hollow channel in any organ or structure of the body

absorption and elimination takes place in the:

large intestine

Organs that secrete and produce substances that assist with digestion

liver, gall bladder, bile duct, pancreas

longitudinal muscle

muscle fibers aligned lengthwise

The _____ & ______ secrete material into the small intestine to help with digestion.

pancreas and gallbladder

Four mechanisms are involved in nutrient absorption:

passive diffusion, facilitated diffusion, active transport, and endocytosis.

digestion and absorption takes place in the:

stomach and small intestine

In the mouth, food is mixed with saliva for lubrication. Salivary amylase begins:

the digestion of starch.

submucosa

the layer of loose, fibrous connective tissue under the muscous membrane

Ingestion takes place in:

the mouth and esophagus

The GI tract is a tube that can be divided into regions:

the mouth, esophagus, stomach, small intestine, large intestine, and rectum.

Peristalsis:

the movement of food using muscular contractions

absorption

the movement of molecules across the lining of the GI tract and into circulation.

catalyze

to speed up a chemical reaction