Gastrointenstinal

Functions of Digestive system?

Ingest, Digest, Absorb (move nutrients into blood), Defecate

2 main groups of digestive organs?

Alimentary Canal. Accesssory Digestive

Organs that ingest, digest, obsorb, and defecate are part of THIS continuous hollow tube.

What is the Alimentary Canal?

What are accessory digestive organs?

Teeth, tongue, etc... assist digestion

Organs of Alimentary canal?

Mouth, Pharynx, Esophagus, Stomach, Small Intestine, Large inestine, Anus

Essential processes of GI Tract? (6)

Ingestion, Propulsion, Food breakdown: mechanical breakdown, Food breakdown: digestion, Absorption, Defecation

Methods of digestive Propulsion process?

Peristalsis - contraction/relaxation that squeeze food along GI tract... Segmentation - movement of materials back/forth to foster mixing in small intestine

Types of mechanical breakdown in GI tract?

Mixing food in mouth, Churning food in stomach, segmentation in small intestine

Purpose of mechanical breakdown?

prepares food for further degradation by enzymes

What is digestion?

chemical breakdwon by enzymes

What is GI absorption? i.e. What cells absorb nutrients?

nutrient absorption into blood or lymph via mucosal cells

What is defecation?

removal of indigestible substances as feces

First stage of digestion?

Salivary amylase begins starch digestion in mouth

Does absorption occur in mouth?

no

Functions of Pharynx and esophagus?

swallowing (pharynx), and passageways to stomach. NO DIGESTIVE FUNCTION

Phases of swallowing? (deglutition)

Buccal phase, pharyngeal-esophageal phase

Which stage of swallow is voluntary?

Buccal phase - in mouth, food formed into BOLUS, bolus forced into pharynx

What structure forces the food bolus into pharynx during buccal propulsion phase?

tongue

How is the food bolus transported during pharyngeal-esophageal phase of propulsion?

peristalsis

what passageways are blocked during pharyngeal-esophageal phase of propulsion?

nasal and respiratory

How does the food bolus enter stomach? When?

cardioesophageal sphincter opens when food presses against it... at end of phayngeal-esophageal phase

Functional fluids/molecules involved in chemical breakdown during digestion?

Gastric juice produced by gastrin hormone - Protein-digesting enzymes, mucus, hydrochloric acid

How is gastric juice regulated/released? What hormone?

neural/hormonal... presence of food OR rising pH causes releases of GASTRIN HORMONE

What does HCL do in stomach?

increases acidity --> activates pepsinogen to pepsin (protein breakdown) and provides hostile environment for microorgansims

What breaks down starches?

Salivary amylase in mouth

what breaksdown proteins?

pepsinogen -> PEPSIN

What digest milk?

Rennin... ONLY in infants, NOT present in adults

True/False - absorption of food bolus begins in stomach

False. Alcohol and spirin are only items absorbed in stomach

Stages of propulsion in stomach? (3)

Peristalsis - force food past pyloric sphincter. Grinding - pylorus meters out chyme into duodenum (3mL at a time). Retropulsion - peristaltic waves close sphincter, forcing contents back into stomach

What is the most vigorus form of peristalsis?

Grinding

How long does it take for the stomach to to empty?

4-6 hours

Where does chyme breakdown and absorption begin?

small intestine

Functions of intestinal enzymes?

break double sugars into single. Complete some protein digestion. Digest all food groups

_________ enzymes play major role in digestion of fats, proteins, and carbs?

Pancreatic

How does the small intestine environment allow pancreatic enzymes to operate?

Alkaline (bicarbonate rich) content neutralizes acidic chyme

What stimulates pancreatic juice release?

VAGUS, secretin and cholecystokinin (CCK) hormones

Functions of bile?

fat emulsifier - needed for fat absorption and vitamins

where and how is bile secreted?

from liver and gallbladder via secretin and CCK hormones

Where is water absorbed?

length of small intestine

How are substances absorbed in digestion?

mostly via active transport

How are lipids absorbed in digestion?

diffusion

______ is the major means of moving food

Peristalsis

function of segmental movements?

mix chyme with digestive juices, aid in propulsion

How are nutrients digests in large intestine?

bacteria ... NO digestive enzymes produced in large intestines

What materials are absorbed in large intestines?

water, vitamins, ions

matierals contained in feces?

undigested food residues, mucus, bacteria, water

Most frequent movements in large intestines?

Haustral contractions

What causes defecation reflex?

feces at rectum

Process of defecation?

Internal sphincter relaxed, defecation occurs with relaxation of external anal sphincter