TEAS 7 Digestive/gastrointestinal system

anatomy

Function

Organs take in food & liquids and break them down into substances that can be used for energy, growth, & tissue repair

4 functions of gastrointestional system

1. Ingestion

Taking in food (Eating)

2. Digestion

Biomolecule polymers break down food into building blocks

3. Absorption

Absorbs nutrients to be delivered

4. Elimination

Waste is removed

Types of digetsion

Mechanical:

Physically breaking down food into smaller particles (Chewing/ Mastication)

• Skeletal muscles of mouth & pharynx aid in swallowing (deglutition)

• Peristalsis: Involuntary process that constricts & relaxes to move food from pharynx ^ to esophagus to stomach (extra muscle layer in stomach helps churn food)

• Segmentation: Process that takes chyme (partially digested food) through the small intestines

-Chyme: Food bathed in gastric juices

-Movement along digestive tract is also controlled by gastroesophageal sphincter, pyloric sphincter, & anal sphincter

• Lower gastroesophageal sphincter: separates esophagus from stomach

• Pyloric sphincter: Separates stomach from small intestine, prevents backflow into stomach

Chemical digestion

Enzymes break down nutrients into smaller molecules

• Saliva has enzymes, solutes, and buffers (which neutralize acidity in mouth that protects teeth)

• Hydrocloric acid(HCL): acidic solution of the gas hydrogen chloride in water

• Pepsin: Chief digestive enzyme that breaks down proteins into polypeptides

-Dry mouth: Condition of a lack of sufficent saliva (Bad for dental health)

Epiglottis & esophagus

Esophagus: takes down food, produces mucus as lubricant to aid

Epiglottis: Flap that prevents food from going down trachea

Stomach

Below esophageal sphincter

4 main parts:

1. Cardiac region: food is emptied into stomach

2. Fundus: superior region of stomach (most central to body) J shape to the right

3. Pylorus: funnel shaped region

4. Pyloric sphincter: releases chyme to small intestines

Another part of stomach

• Gastric folds (rugae): mucosa that allow the stomach to stretch and expand

• Can store 2 liters of food and liquid

Small Intestines

1. Duodenum- shortest segment of small intestines

• Chemical digestion of chyme

• Breaksdown fats, proteins, & carbs

• Absorbs iron + other minerals

2. Jejunum- middle segment

• Absorbs nutrients

• Carbs & proteins absorbed into bloodstream

• has VILLI: Tiny hair like projections that line the intestines & help abosrption into blood stream

3. Ileum- final segment

• Absorbs nutrients

• Vitamin B12, bile salts, & products of digestion absorbed

Mnemonic

Digestive: Duodenum

Juices: Jejunum

Intake: Ileum

Large intestines

1. Ascending colon (Cecum)-first segment

• Absorbs water and salts

• Solidify waste into formed stool

2. Transverse colon - longest, most mobile part

• Storage site for digested food

• More absorbtion of water & salts

3. Descending colon- descending segment

• Carries solid waste toward rectum

• More absorption of water & minerals

• Stores feces until defecation

Haustra: pouch like sacs that give large intestine its segments

Mnemonic:

Ascending Absorbs

Transverse Transports

Descending Drives Down

Water absorption large intestines

Diarrhea: Too little water absorbed

Constipation: Too much water absorbed

Elimination

Rectum

Stores feces until expelled through the anus

Gastric glands in mucosa of the stomach

1. Endocrine cells (G cells)

• Gastrin (hormone): Stimulate gastric glands to secrete pepsinogen and HCI

2. Parietal cells

• Secretes intrinsic factor, required for absorption of B12 in the small intestine

3. Chief cells

• Secretes acidic enviorment activates pepsinogen

• Pepsin: active form of pepsinogen, digestive enzyme that breaksdown proteins into smaller peptide chains

4. Mucous cells

• Secrete bicarbonate- containing mucus that protects stomach from acidity & digestive enzymes

Liver

Carbohydrate & protein metabolism

• Creates bile to help breakdown lipids in small intestines

Bile: yellow-green solution of bile salts, pigements (mainly bilirubin), cholesterol, & electrolytes

Gallbladder

Stores bile produced by liver

Pancreas

Produces pancreatic juices to help neutralize chyme

• triangle shape

Hormones

Gastrin

• Found in G cells of the stomach

• Stimulates gastric glands to secrete pepsinogen & HCI

Cholecytokinin

• In I cells of of duodenum & jejunum

• Digesting fats & proteins & stimulating the gallbladder to release bile

Secretin

• Found in S cells of duodenum

• Regulates pH by inhibiting gastric acid secretion & stimulating bicarb production

Insulin

• Found in beta cells of the pancreas

• Glucose metabolism & stores glucose as glycogen

Glucagon

• Found in alpha cells of pancreas

• Raises blood glucose levels

Enteric nervous system

Nuerons that line the GI tract and control functions of digestive system