BIO202 Unit 5 Lab 9 - Digestive System

Alimentary canal

digestive tube that extends from the mouth to the anus

Tunics (layers) of alimentary canal wall

-mucosa (innermost layer)

-submucosa

-muscularis externa

-serosa (outermost layer)

Order that food passes through the alimentary canal

mouth -> pharynx -> esophagus -> stomach -> small intestine -> large intestine -> anus

Ingestion

Intake of food

Mastication

the process of chewing

Peristalsis

Involuntary waves of muscle contraction that keep food moving along in one direction through the digestive system.

Segmentation (of digestion)

smooth muscle back and forth contractions to mix and break food further down

digestion

Breakdown of food substances into simpler forms that can be absorbed and used (polymers -> monomers)

mechanical digestion

Physical breakdown of large pieces of food into smaller pieces

chemical digestion

Process by which enzymes break down food into small molecules that the body can use

salivary amylase

Enzyme in saliva that breaks down carbohydrates

Oral cavity

The part of the mouth behind the gums and teeth

-roof formed by hard and soft palates and

- below by the tongue and by the mucous membrane connecting it with the inner part of the mandible.

Oral cavity - vestibule

Space between the lips or cheeks and the teeth.

Deciduous Teeth

baby teeth (first to appear), 20 total

Permanent Teeth

adult teeth, 32 total

Teeth - Incisors

-chisel shaped for cutting & clipping

Teeth - Canines

-Fanglike teeth that tear or pierce

Teeth - Bicuspids (premolars) & Molars

-Broad crowns, rounded cusps for grinding/crushing

Tooth - root

-portion embedded in jawbone

-Anchored in bony socket by cementum and periodontal ligaments

Tooth - pulp

consists of nerves, blood vessels, and loose connective tissue

Tooth - crown

Exposed part of the tooth above the gingivae or gums; covered with enamel.

Tooth - enamel

hardest substance in the body

Tooth - dentin

Bone like material making up most of tooth, under the enamel

Tooth - root canal

extension of the pulp cavity into the root

Tooth - neck

connects crown to root

Saliva - composition

- 97-99.5% water;

- pH 6.75-7 (slightly acidic);

- includes amylase (breaks down carbohydrates/sugars)

Bolus

food after it has been chewed & mixed with saliva when it is swallowed (after it leaves the oral cavity)

deglutition

process of swallowing

Esophagus

tube that connects the pharynx to the stomach through the diaphragm muscle

Where does mechanical digestion take place?

In the mouth (chewing), stomach (churning), and intestines (segmentation)

Where does chemical digestion take place?

In the mouth (saliva), stomach (acid), and intestines (pancreatic enzymes and bile)

Stomach - pH

- 1.5-3.5

- due to hydrochloric acid

stomach - sphincters

1. cardiac/cardioesophageal (top - at entrance of stomach)

2. pyloric (bottom - at entrance to small intestine)

intrinsic factor

A substance produced by the mucosa of the stomach and intestines that is essential for the absorption of vitamin B12.

pepsinogen/pepsin

Hydrochloric acid activates the inactive enzyme __________ to the active form ________, which digests protein.

gastric glands

exocrine glands in the stomach wall that secrete gastric juice (hydrochloric acid & pepsinogen) into the stomach

Gastric Glands - Parietal Cells

secrete HCl (hydrochloric acid) and intrinsic factor

Gastric Glands - Chief Cells

secrete pepsinogen (inactive enzyme)

Hydrochloric Acid (HCl) function (in stomach)

low pH which activates inactive enzyme pepsinogen into pepsin for protein digestion

Chyme

Partially digested, semiliquid food mixed with digestive enzymes and acids leaving the stomach.

heartburn

-a painful burning sensation in the chest caused when stomach acid regurgitates into esophagus

•Likely with excess food/drink, extreme obesity, pregnancy, running

gastroesophageal reflux disease (GERD)

chronic heartburn in which acidic stomach contents leak into the esophagus repeatedly, causing pain and damaging the esophagus

gastritis

inflammation of the lining of the stomach

gastric ulcer

ulcer located in the stomach

-most caused by H. pylori bacteria, some by NSAIDS (aspirin)

symptoms: burning/gnawing/dull pain in upper abdomen, nausea, vomiting, heartburn, bloating, belching, loss of appetite, black or tarry stools (from blood), weakness, fatigue

rugae

the folds in the mucosa lining the stomach

goblet cells

secrete mucus which helps to protect the stomach lining from the low pH due to presence of HCl

length of time food stays in stomach

4-6 hours

small intestine

Digestive organ where most chemical digestion and absorption of food takes place

small intestine - divisions

1. Duodenum

2. Jejunum

3. Ileum

Structural modification of small intestine for nutrient absorption

circular folds, villi, microvilli (brush border)

small intestine - circular folds

Permanent folds (~1 cm deep) that force chyme to slowly spiral through lumen, allowing more time for nutrient absorption

small intestine - villi

Fingerlike extensions of the intestinal mucosa that increase the surface area for absorption

Small intestine - microvilli (brush border)

- folding of the apical surface of each epithelial cell (upon the villi)

- contain enzymes for carbohydrate and protein digestion

Diverticula

Herniations, or outpouchings, of the walls of the large intestine

Diverticulosis

presence of diverticula

Diverticulitis

inflammation of the diverticula in the colon that may rupture & leak into the peritoneal cavity

Length of time chyme travels in small intestine

3-6 hours

Large Intestine - function

Absorbs water, salts & some vitamins; forms feces

Large Intestine - divisions

1. cecum, 2. colon, 3. rectum, 4. anal canal

Appendix - location

A small, fingerlike extension of the cecum

Appendicitis

•acute inflammation of appendix; usually results from a blockage by feces that traps infectious bacteria

-treatment: appendectomy (surgical removal of appendix)

Gall bladder - function

stores bile from liver

Bile

yellow-green, alkaline solution made by the liver, stored in the gall bladder and functions to break down/emulsify fats

Diarrhea

frequent passage of loose, watery stools

Constipation

Hard, slow stools that are difficult to eliminate; often a result of too little fiber in the diet

Cirrhosis of the liver

a chronic liver disease characterized by the replacement of healthy liver tissue with scar tissue, leading to impaired liver function and potentially liver failure

-symptoms can include fatigue, loss of appetite, jaundice (yellowing of the skin and eyes), abdominal swelling (ascites), and easy bruising or bleeding

Location of digestion - CARBOHYDRATES

mouth and small intestine

Location of digestion - LIPIDS

mouth, stomach, small intestine

Location of digestion - PROTEINS

stomach and small intestine

Defecation

elimination of feces from the digestive tract through the anus

Macromolecules

Macromolecules - CARBOHYDRATES

sugars & starches

monomer = monosaccharide (example: glucose)

Macromolecules - LIPIDS

fats, triglycerides, phospholipids, steroids

Smallest unit (not a true monomer) = triglycerides

Macromolecules - PROTEINS

monomer: amino acids

Aerobic Cellular Respiration stages/metabolic pathways

1. glycolysis (breakdown of glucose)

2. Krebs cycle

3. electron transport chain/ETC

High-density lipoprotein (HDL)

blood fat that helps transport cholesterol out of the arteries, thereby protecting against heart disease

"good cholesterol" - remember H = halo

low-density lipoprotein (LDL)

blood fat that transports cholesterol to organs and tissues; excess amounts result in the accumulation of fatty deposits on artery walls

"bad cholesterol"

esophageal cancer

cancer of the esophagus often caused by GERD, smoking, heavy alcohol consumption

BMI (body mass index)

a measure of body weight relative to height

BMI - obese

over 30

Disorders associated with obesity

- Diabetes

- Hypertension

- Coronary heart disease

- Cancer

- Premature death

- Sleep apnea

- Stroke

- Asthma

- Osteoarthritis, etc.

anabolic reactions/ anabolism

Use energy to convert smaller molecules into larger molecules (monomer -> polymer)

catabolic reactions / catabolism

release energy by breaking down large molecules into smaller ones (polymer -> monomer)

Metabolism

All of the chemical reactions that occur within an organism

Cystic Fibrosis - digestive system effects

-Thick mucus in pancreatic ducts block enzymes to small intestine responsible for digestion of nutrients which results in loss of ability to break down fats, fat-soluble vitamins, etc.