Digestive System Flashcards by Kizzie Fish

What is digestion?

The process where large, complex food substances are broken down into small, simple, soluble substances that can be easily absorbed

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What is the function of the GI tract (digestive tract)?

Hollow tube

Approx 10m long

Travels length of body starting at the mouth, passing through the thorax, abdomen, pelvis and ending at the anus

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What is the function of the accessory organs?

Contribute to digestive process

Passes various secretions into digestive tract

Generally situated outside DT- secretions pass through ducts to enter main tract

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Name examples of organs of the DT…

Stomach
Mouth
Oesophagus
Small/large intestine 
Rectum
Anus

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Name examples of accessory organs…

Liver
Pancreas
Gall bladder
Salivary glands

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What allows for ingestion to take place?

Mouth- food is taken into the oral cavity

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What enables propulsion to take place?

Movement by Peristalsis

Includes oesophagus, stomach, small/large intestine

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Define digestion…

Food is broken down mechanically and chemically by enzymes

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What enables digestion to take place?

Mouth- tongue and teeth (mechanical) and saliva (chemical)

Stomach

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What allows absorption to take place?

Small intestine

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What is absorption?

The movement of digested molecules across the GI tract into the blood

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What is assimilation?

Movement of molecules from the blood to the cells

Then become a part of body tissues

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What enables elimination to take place?

Rectum and anus- defecation

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What is the function of the mouth?

Contains teeth, tongue, and salivary glands

Allow food to begin the digestive process- breaking down food to smaller pieces, mixes with saliva and manipulates it so it can be swallowed

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What enzyme is found in saliva?

Salivary Amylase- initiates starch digestion

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What are the functions of saliva?

1) antibacterial effect eg enzyme lysozyme (destroys bacteria)
2) washes away food that may be a source of bacteria
3) acting as buffer- contains bicarbonate (neutralises acids, preventing dental issues)

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How is food swallowed?

Bolus (ball of food) is formed

Directed by tongue around the mouth until it can be swallowed

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What is swallowing?

Series of movements transporting food from the mouth to the pharynx into the oesophagus

How is the pharynx involved in respiration?

Air enters pharynx when heading into the lungs while food passes through here and enters the stomach

What structure prevents food from entering the trachea?

Epiglottis

What are the 4 layers of the wall of the digestive tract?

1) mucosa
2) submucosa
3) muscularis
4) serosa

What is the mucosa?

Innermost layer of DT

Largely made of epithelial tissue

Ingested food is in direct contact with this layer- lot of wear and tear

DT- folded to provide larger SA for digestion/absorption

(In intestine) forms finger like projections-villi

What is the function of the mucosa?

Specialised cells scattered throughout- secretes mucus, lubricating/protecting gut lining

Also cells secreting chemicals needed for digestion

Thin epithelial layer provides route for absorption

What is sub-mucosa?

Layer of loose connective tissue

Contains nerves, blood and lymph vessels

What is the function of the sub-mucosa?

Blood supply enables nourishment of tissues + transports products of digestion Primarily involved in absorption of fat (Lymph vessels- involved in immune system)

What is the muscularis?

3rd layer of DT Contains 2 layers of smooth muscle- circular and longitudinal with nerve tissue (plexuses) between them

What is the function of the muscularis?

Coordinated contraction of it- rhythmic peristalsis Includes skeletal muscle (in mouth, pharynx and upper part of oesophagus) involved in voluntary swallowing

What is the serosa?

Outer coat Contains loose fibrous tissue and nerve, blood and lymph vessels

What is the function of serosa?

Protection (of outer layer)

What is the oesophagus?

Straight, muscular tube connecting pharynx to stomach Muscular wall containing mucous glands

What is the function of the oesophagus?

Mucous glands in walls secrete mucus, keeping lining moist/lubricated- allows bolus to slide down smoothly Longitudinal/circular muscles lining walls contract-move bolus along- Peristalsis

What prevents food going back into the oesophagus?

Oesophagus has upward curve Cardiac sphincter/lower oesophageal sphincter at stomach entrance- opens allowing bolus to enter and closes preventing reflux

What is the stomach?

Large, j-shaped bag Lies just under diaphragm in upper left side it abdominal cavity

What are the 3 parts of the stomach?

1) fundus- lies near cardiac sphincter 2) body- middle part 3) antrum- lower part containing pyloric sphincter

What are rugae?

Folds in the stomach (mucosa/sub-mucosa) - flatten out and allow for the stomach to expand

What are the specialised cells in the stomach?

1) goblet cells- produce mucus to coat/protect stomach lining 2) parietal cells- produce HCl and intrinsic factor 3) G cells- produce hormone gastric, regulating gastric secretions 4) chief cells- produce pepsinogen (inactive precursor to pepsin) chemically breaking down protein molecules

What are the 3 sections of the small intestine?

1) duodenum 2) jejunum 3) ileum

What is the function of the duodenum?

Short c-shaped tube Contains glands- secrete an alkaline mucus used to neutralise acidic chyme produced in the stomach Region where large ducts, liver + pancreas connect

What is the major role of the small intestine?

Absorb nutrients that have been broken down from food Absorbed via active transport and diffusion

What adaptations does the small intestine have for nutrient absorption?

1) large SA- folds of intestinal wall, villi and microvilli | 2) network of capillaries- short distance for nutrients to travel into bloodstream, aiding absorption

What are the functions of the large intestine?

1) absorption of water/electrolytes 2) storage/elimination of faeces 3) bacteria digest some polysaccharides 4) bacteria produce vitamins (K+B) 5) appendix has immune function

What is the function of the liver?

Makes bile- emulsified fat/aids fat absorption Bile- pH 8

What is the function of the gall bladder?

Stores bile- secretion into the duodenum

What is the function of the pancreas?

Makes pancreatic juice containing digestive enzymes/bicarbonate ions pH 8