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Flashcards in GI Structure Blatter Deck (36):

What is the ultimate input of all energy

Food intake is all energy input


What requires energy output

Internal work- heat pdtion, temp reguluation

External work- skeletal muscles


Neutral Balance
Positive Energy Balance
Negative Energy Blanace

1. Neutral- homeostasis where energy input= output

2. Positive- Energy input> output so storage as adipose and weight gain

3. Negative- Energy output> input so we use storage. 1st carbs, then fat, then proteins


How does GI contribute to homeostasis and why (2)?

Transfer water, electrolytes and nutrients (carbs, lipids, proteins, vitamins, cofactors) from external to internal to maintain constant internal environment and distribute energy to organism


Overall Function of the GI system

1. Digestion and absorption
2. Excretion of waste
3. Fluid electrolyte balance
4. Immune function
5. None immune defense- epithelial cell permeability, secretions, peristalsis


What is the immune system in the gut? Functions?

GALT- gut-associate lymphoid tissue- important for protection against microbial pathogens and permits immunologic tolerance to potentially immunologic dietary substances


4 basic digestive processes

1. Motility- myscular contractions that move food
2. Secretion- exocrine secrete digestive juices and endocrine- hormones that regulations GI tract
3. Digestion- degrade to carbs, fat and proteins
4. Absorption- Absorable units plus water, electrolytes, vitamins go from lumen to circulatory tract


Difference in endocrine and exocrine in GI

Exocrine- secrete digestive juices

Endocrine- secretes enzymes that regulate GI


Accessory digestive organs (4)

1. Salivary glands
2. Exocrine pancreas
3. Biliary system- gallbladder and liver
4. Endocrine gland and cells


4 common features throughout the GI tract

1. Mucosa
2. Submucosa
3. Muscularis externa
4. Serosa or adventitia


What are the parts of the the mucosa?

1. Epithelial- protection, secretion and absorption
2. Lamina propria- CT, lymphoid tissue and glands
3. Muscularis mucosae- smooth muscle that increases SA
4. Exocrine cells
5. Endorcine/pacrine cells


Parts of the submucosa

CT, large blood vessels, submucosal glands, and lymphoid tissue

Submucosal nerve plexus (Meissners plexus)


Parts of the mescularis externa

contractions that move mix aboral

two layers- inner circular and outer longitudinal and between the layers is the Myenteric (auerbachs plexus)


Function of the serosa

CT that covers the GI tract with squamous moesthelial cells. Secretion of serous liquid is lubrification and prevents friction


Name the sphincter between each part of GI tract

Mouth/pharynx--> pharyngoesophageal sphincter-- esophagus-- gastroesophageal sphincter--- stomach-- pyloric-- small intestine- ileocecal sphincter- large intestine- internal/external anal sphincter


Origination of GI oscillations

The slow waves originate at the intestinal pacemakers (Cajal) and control the timing and force of contractions... activity is autonmous but can be modulated by neural and hormonal


Explain the break down of neural regulation in the GI

Somactic- oral phase of swallowing and tonus of external anal spinchter



Function of intestinal smooth muscle cells

1. Effector organ of GI motility
2. Intestinal pacemaker- responsible for contractile activity


Explain function, location of synthezise and transport of hormones in the GI tract

Function- regulate contractility and secretions

Synthesized and released by endocrine glands

transport via blood stream to target sites


Primary Stimulation

1. G-cells of the stomach
2. stimulated by protein in the stomach, stretch, and nerves

3. Stimulates HCL and cheif cells
Trophic to stomach and SI
Enhances gastric motility
Constricts the pyloric sphincter
causes gallbladder contractions
Induces colonic mass movements
Enhances pancreatic secretion


1. Source
2. Primary stimulus
3. Functions

1. S Cells in the Duodenum and jejunum
2. Stimulus is acid in the duodenum
3. Function- stimulates aqueous NaHCO secretion by pancreatic ducts
Stimulates NaHCO3 rich bile from the liver
INhbits gastric acid secretion
Trophic to exocrine pancreas


1. Source
2. Stimulus
3. Function

1. I cells in the duodenum or jejunum
2. Fat, proteins in the doudenum or nerves
3. Function- Stimulates digestive enzymes secretion by pancreatic ancinar cells
Stimulates pancreatic NaHCO3 secretion
causes gall bladder secretions


Gastric Inhibitory Peptide

1. Source K cells in duodenum and jejunuum
2. Fat, glucose, acid, hypertonicity and distension
3. Function- inhibit gastric acid secretion
Stimulates insulin secretion by endocrine pancreas
Inhbitits gastric emptying


About of immune cells in GI tract

About 1/2 of the body's total mass of immune cells


Which and from where are pancreatic hormones released

Insulin, glucagon, and somatostatin from the islets of langerhans in the pancreas


What happens in catobolism?

Oxidative degradation of complex nutrient molecules (Carb,lipids, and proteins) into simple molecules like lactic acid, CO2, ammonia, and urea

Usually exergonic and releases energy in the form of NADH/FADH


What happens in anabolic metabolism

Synthetic process where a complex biomolecule is made from simple precursors (sugar, nitrogenous bases, AA, Fatty acids).

Usually endergonic and new covalent bonds are formed


Explain the basic steps of catobolism in the GI tract

1. GI takes up and degrades macromolecules and absorbs building blocks (hydrolysis of complex molecules)
2. Within the cells- the absorbed building blocks are further degraded (conversion of building block like AA, monosacc, glyercol to acetyl CoA)
3. AcCOa processed in TCA + oxidative phosphorylation make CO2+H20 and ENERGY (oxidation of acetyl CoA)


Where is a bulk of digestion and what absorbs it?

In the SI- food is degraded by digestive enzymes and absorbed by epithelial cells

When digested nutrients enter the hepatic portal vein and travel to the liver and then through the blood


Overall efficiency and enzymes for degradation of protein

Over only 5% of enzymes lost in feces

Proteins are degraded by endopeptidases (internal large cleavage) or by exopeptidases- 1 AA at a time of the end-- exopeptidases can be carboxypeptidases or aminopeptidases


3 phases of protein digestion

Gastric, pancreatic, and intestinal


Discuss gastric phase of protein digstion

Stomach has gastric juices that HCl and members of the pepsin protease family.

Pepsin releases large peptide products and some AA which stimulates the release of CCK and initiates pancreatic phase of digestion


Discuss pancreas phase of protein digestion

Pancreas has two histologically different areas
1. Islet of langerhan the releases insulin and glucogon
2. Exocrine pancreas is important for DIGESTION and it secretes 1.5L at pH 8 of pancreatic juices with hydolytic enzymes into the duodenum everyday


Discuss the intestinal phase of protein degradation

Lining of the intestinal lumen have endo and aminopeptidases activities that further degrade peptides to AA which are absorbed


How are monosacc, disaccs, and polysaccs absorbed

Monosacc- directly by the intestinal cells
diacc- digested into monosacc by the intestinal cells
Polysaccs (starch and glycogen) need to be reduced to smaller building blocks


All parts involved in carb digestion

Mouth-starch and glycogen degraded by alpha-amaylase in salive makes glucose, disacc, and trisaccs

SI- alpha-amlyase makes glucose, disaccs, and trisaccs.
They are further degraded at the intestinal cells by alpha glucosidase; some disaccs have specific enzymes for degradation (lactase and sucrose)

Oligosacc. not yet degraded by amylse or intestinal cells reach the ileum where they are degraded by bacteria and produce fatty acids, lactate, H2 and methane and CO2