Gastrointestinal: Anatomy Flashcards by Josh Cowling

What are the 2 paths for GI regulation?

Neural and endocrine

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How is food intake regulated? (2)

Is not based on homeostasis

Maximise absorption - whether nutrients needed or not

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What are the 2 major parts of the GI system?

GI tract - organs joined to process food

Accessory glands - secrete fluids and enzymes

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What does the GI system supply the body with? (3)

Water
electrolytes
Nutrients

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How is the GI system controlled? (2)

Hormonal and nervous system

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What is an autotroph?

Synthesise all essential organic nutrients from inorganic sources

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What is a heterotroph?

Have limited synthetic abilities - require organic compounds in the form of food

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What are the 8 essential amino acids?

Tryptophan 
Methionine
Threonine
Phenylalanine
Valine
Leucine
Isoleucine
Lysine

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What are the 3 macro constituents?

Carbs
Proteins
Lipids

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What are the 3 micro constituents?

Vitamins
Minerals
Water

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What are the 3 properties of the gut tube?

Hollow tube
15ft long
Open to the outside world

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What are the 4 basic processes of the gut tube?

Digestion
Absorption
Motility
Secretion

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What is the anatomy of the GI tract? (6)

Oral cavity
Oesophagus
Stomach
Small intestine
Large intestine
Rectum

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What are the 4 layers of the digestive tract?

Mucosa - lining
Submucosa - layer of connective tissue
Muscular externa - smooth muscle fibres
Serosa - outer layer of connective tissue
(In to out)

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What is the mucosa made up of? (3)

Mucous membrane
Lamina propria
Muscular mucosae

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What is the role of the mucous membrane in the mucosa? (4)

Epithelial cells layer (enterocytes):

absorptive
exocrine
goblet
endocrine

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What is the lamina propria? (2)

Connective tissue underlying mucous membrane

Blood vessels, nerves and lymphatics

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What is the role of muscular mucosae? (3)

Thin layer of smooth muscle
Lots of folds
Promotes movements

What is the submucosa made up of? (2)

Connective tissue

Enteric nervous system

What is the role of connective tissue in the submucosa? (3)

Provide GI tract with elasticity and distensibility
Tolerate stretch
Contain larger blood and lymphatic vessels

What is the role of the enteric nervous system in the submucosa? (3)

Sensory, motor and inter neurone
Regulates GI functions
Output from enteric goes to effector cells

What is the makeup of the muscularis externa? (3)

Inner layer of circular muscle
Outer layer of longitudinal muscle
Contraction - regulates movement of the gut

What is the makeup of the serosa? (2)

Inner layer - fibrous tissue, structural support

Outer layer - epithelial tissue, secretions

Where is HCl secreted from?

Pits

What are the organs of the GI tract? (6)

``` Pharynx Oesophagus Small Intestine Colon Rectum Anus ```

What is the mouths role in digestion? (2)

``` Mastication is the start - chewing Saliva secretion (lubricant) and digests (amylase) ```

What is the oesophagus' anatomy? (2)

Top 1/3 - skeletal muscle | Bottom 2/3 - smooth muscle

Describe the 3 stages of the swallowing reflex?

1. Tongue pushes bolus against back of mouth, trigger 2. Upper esophagus sphincter relaxes while epiglottis closes (keeps airways closed) 3. Food moves downwards into oesophagus by peristaltic waves and gravity

What is the function of the stomach in digestion? (4)

> Stores food after it has been swallowed > Secretes gastric juice > releases food into intestine slowly > regulated by pyloric sphincter

What is the anatomy of the stomach? (4)

Fundus Body Antrum Rugae (curls)

Why is the stomach acidic? (4)

Necessary for pepsinogen activation Kills bacteria Denatures proteins Gastric mucosal barrier (bicarbonate and mucus layer)

What are gastric pits? (4)

Secrete enzymes - pepsinogen (chief cells) - Hydrogen ions (parietal cells) - Gastrin (G cells) - Mucus (neck cells)

What is the structure of the small intestine? (4)

Coiled, hollow 8-10ft long Between stomach and large intestine 3 divisions: duodenum (top, excretes), jejunum (middle, absorbs), ileum (bottom, absorbs)

What is secreted into the duodenum? (2)

``` Pancreatic juice (digestive enzyme and bicarbonate) Bile (salts which aid fat digestion) ```

What is the anatomy of the small intestine wall? (4)

Villi Blood vessels Lacteal (absorption) Microvilli

What are the crypts of Lieberkuhn?

Epithelial cells in crypts secrete bicarbonate

What is the role of the liver in absorption? (2)

Absorbed nutrients in the blood travel to liver before general circulation Liver detoxifies

What is the blood supply to the liver? (2)

Hepatic portal vein from small intestine | Hepatic artery from aorta

What is the large intestine made up of? (4)

Cecum Colon Rectum Ileocecal sphincters between ileum and colon

What are the functions of the large intestine? (3)

Concentrates wastes into faeces Absorption of most water Stores faeces until defecation

What are the 4 sections of the colon?

Ascending colon Transverse Descending Sigmoid

What is the relationship between the rectum and the anus?

Colon empties into rectum, then faeces through anus

What are the 2 types of sphincters in the anus?

Internal anal sphincter - smooth muscle External anal sphincter - skeletal muscle Must relax both to poo