Physiology Flashcards by Jan Böll

What are the main compartments of the digestive tract?

Oral cavity
Pharynx
Oesophagus
Stomach
Small intestine
Colon
Rectum

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What are accessory organs of the digestive tract?

Tongue
Teeth
Salivary glands
Pancreas
Liver
Gallbladder

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Active process of food entering the oral cavity

What is the term for this?

Ingestion

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Crushing, shearing and chewing of food

What is the term for this?

Mechanical digestion and propulsion

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Chemical breakdown of food into small organic and inorganic molecules

What is the term for this?

Chemical digestion

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Release of water, acids, enzymes, buffers and salt

What is the term for this?

Secretion

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Movement of organic molecules, vitamins, electrolytes, minerals and water across digestive epithelium

What is the term for this?

Absorption

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Elimination of waste products from body

What is the term for this?

Defecation

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→ Caustic effects of digestive acids and enzymes
→ Mechanical stress
→ Bacteria

What do the above provide to the digestive tract?

Protection

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What is the function of the oral cavity in digestion?

Sensory analysis of food before swallowing
Mechanical digestion (teeth, tongue, palatal surfaces)
Lubrication → mixing food with saliva and mucus
Limited chemical digestion of carbs and fats

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How much saliva do the salivary glands produce daily and what does it consist of?

1-1.5l per day of saliva

→ 99.4% water, 0.6% electrolytes, buffer, glycoproteins, enzymes, antibodies, waste

→ Keeps oral surfaces clean

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What is the function of the pharynx in digestion?

Muscular propulsion of bolus into oesophagus

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What is the function of the oesophagus in digestion?

Actively moves swallowed food to stomach

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How long is the oesophagus usually?

Approx. 25cm

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What are the main characteristics of the stomach?

Receives food from oesophagus → temporary storage
Mechanical digestion → muscle contraction
Chemical digestion → acids and enzymes
Expendable tube-like organ
Shaped like a “J”

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Which organ is shaped like a J?

The stomach

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Where does 90% of the nutrient absorption happen in the body?

Small intestine

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How long is the small intestine usually?

Approx. 6 meters

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What are the 3 segments of the small intestine?

Duodenum

Jejunum

Ileum

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What are characteristics of the duodenum of the small intestine?

first 25cm → mixing bowl

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What are characteristics of the jejunum of the small intestine?

2.5m → bulk of chemical digestion and nutrient absorption

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What are characteristics of the ileum of the small intestine?

3.5m → controls flow of material to large intestine via ileocecal valve

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What is the name of the valve between small and large intestine?

ileocecal valve

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What are the 4 main layers of the small intestine?

Mucosa (Inner Layer)

Submucosa

Muscular layer

Serosa (outer layer)

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What does the mucosa of the small intestine consist of?

→ Made of epithelium, areolar tissue and m. mucosae → Moistened by glandular secretions

What does the submucosa of the small intestine consist of?

→ Irregular CT → Between mucosa and muscular layer → Contains blood and lymphatic vessels and nerves

What does the muscular layer of the small intestine consist of?

→ Contains smooth muscle cells → Innervated by parasympathetic and sympathetic nervous system

What does the serosa of the small intestine made of?

→ Made of Collagen → Turns into peritoneum

What are the villi and where can they be found?

→ Finger-like projections inside of the small intestine → Increase surface area - e.g. on the plicae

What are the plicae of the small intestine?

→ Folds in small intestines

What shape do the large intestine and rectum have?

Horseshoe shaped

What is the average length and width of the large intestine?

- Average length 1.5m - Average width 7.5cm

What are the 3 main compartments of the large intestine?

→ Cecum: first portion (ileocecal valve💡) → Colon: largest portion → Rectum: last 15cm (Anus = exit of anal canal)

What is the main function of the large intestine?

→ Storage of digestive wastes → Reabsorption of water

What is the main function of the rectum?

→ Temporary storage of faeces

Where is the pancreas positioned and what does it look like?

- Dorsal to stomach - Grey-pink colour - 15cm long - Release of digestive enzymes

What are the 2 main functions of the pancreas?

**Endocrine:** → Secretion of insulin and glucagon into blood stream → Controls blood sugar **Exocrine:** → Secretion of pancreatic juice in small intestine (juice is alkaline mixture of digestive enzymes, ions and water)

Where is the liver positioned and what does it look like?

- Sits in right hypochondriac and umbilical region - Reddish-brown colour - Approx. 1.5kg - Approx. 100k lobules → functional units of the liver - More than 200 different functions

Which organ has more than 200 different functions and approx. 100k lobules (functional subunits)?

the liver

How many lobes does the liver have?

2 (1 right -> bigger, 1 left -> smaller)

What are the 3 main functions of the liver?

Metabolic regulation Hematolic regulation Bile production

Which organ has the largest blood reservoir of the body?

The liver Receives approx. 25% of cardiac output

Where is the gallbladder situated and what is its function?

- Sits in fossa dorsal to liver - Hollow and pear shaped - Storage of bile - Modification of bile

What are the 2 main components of motility in the digestive tract?

Peristalsis and segmentation

What is peristalsis?

- Propulsion of bolus by one contraction after another - Circular muscles - Longitudinal muscles - Continuous process

What is segmentation?

- Bolus fragments or entire bolus is mixed with intestinal secretions - No set pattern - Usually in small intestine, some in large intestine

What coordinates the activity of the digestive glands and the digestion process?

Local factors (e.g. in response to pH) Hormonal mechanisms Neural mechanisms

How long does the absorption in the small intestine usually take?

Approx. 5 hours from duodenum to ileum

What does the large intestine absorb?

- Reabsorption of water → 1,5l of food intake are reduced to 200ml of faeces - Absorption of bile salts, vitamins, organic waste and various toxins

What are carbohydrases?

Enzymes that break bonds between monosaccharides → Maltase, Sucrase, Lactase During digestion

What are proteases?

Enzymes that break bonds between amino acids

What are lipases?

Enzymes that break bonds between fatty acids (glycerides)

- Decrease in division rate of epithelial stem cells - Decrease in smooth muscle tone - Cumulative damage effects become apparent - Increase in cancer rates - Dehydration is common - Direct or indirect influence on digestive system due to changes in other systems What are these effects?

Effects of ageing on digestion

What are the two main states of metabolic activity in digestion?

Absorptive state Postabsorptive state

When does the absorptive state of digestion start and how long does it last?

- Starts immediately after meal - Lasts up to 4 hours

Which hormone is the primary hormone in the absorptive state of digestion?

Insulin

For which purposes do cells absorb nutrients in the absorptive state of digestion?

→ Growth → Maintenance → Energy reserves

What is the postabsorptive state of digestion and how long does it last?

- Time between meals - Lasts up to 12 hours - Period when body has to rely on absorbed nutrients

Which hormones are highly active in the postabsorptive state of digestion?

glucagon glucocorticoids adrenaline GH

What do liver cells ensure during the postabsorptive state of digestion?

→ Transport of energy reserves → Maintenance of blood glucose levels

When do ketone bodies form in the postabsroptive state of digestion?

If carb reserves have been fully depleted

What is a normal pH value in the body?

7.35 - 7.45

What is the pH value when there is acidosis?

< 7.35

What is the pH value when there is alkalosis or basis?

> 7.45

What happens if the pH drops between 6-7?

death

What happens if the pH rises between 7.8-9?

death

What happens in the body if the pH is out of the normal zone?

- Deterioration of CNS → potentially leading to coma - Cardiac contractions grow weak and irregular - Peripheral vasodilation produces decrease in BP and circulatory collapse

What are fixed acids?

→ Once produced they remain in body fluids until eliminated in kidneys → Sulphuric acid, phosphoric acid

What are organic acids?

→ By-products of metabolism → Lactic acid or ketone bodies

What are volatile acids?

→ Can leave body by entering air through lungs → Carbonic acid H2CO3

What does net loss of body minerals in elderly cause?

Decrease in muscle and skeletal mass

What does a decrease in ability to concentrate urine cause in elderly?

Strong increase in H2O loss via urine

What does a decrease in glomerular filtration and functional nephrons cause in elderly?

Decrease in ability to regulate pH

What does a decrease in vital capacity cause in elderly?

Respiratory acidosis

What is the water content of the body at birth?

Approx. 75%

What is the water content of the body in elderly?

Approx. 55% in male, 47% in female