Digestion and metabolism Flashcards by Tae Beamond

What is the structure and function of the eosophagus?

A muscular tube taht takes food from t he pharynx to the stomach.

The lower oesophageal sphincter prevents food from coming bak up from the stomach.

Peristalsis propels food in the right direction.

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What is the structure and function of the oral cavity?

The entry cavity for food. contains the:

> Teeth - perform the mechanical task of chewing

> Tongue - contains small projections called papillae which contain taste buds. The tongue keeps food between the teeth and helps to mix it with saliva to form a bolus.

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What is the structure and function of the salivary glands?

Saliva contains amalayse and lipase to help break food down.

Saliva moistens food for swallowing and dissolves it for tasting.

We have 3 pairs of salivary glands:

Sublingual - under the tongue
Submandibular - under the jaw
Parotid - roof of the mouth

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What is the structure and function of the liver?

Is made of 2 lobes (right and left).

>Filters waste
>Processes nutrients
>Stores fuel for the body
>Makes bile
>Metabolises drugs and hormones
>Bilirubin secretion
>Phagocytosis of bacteria from GIT
>Vit D activation
>Secretes clotting factors
>Cholesterol synthesis

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What is the structure and function of the stomach?

Located in the upper left quadrant of the abdominal cavity, the stomach is a sac that extends from the oesophagus to the small intestine.

> Reservoir for food
Performs mechanical digestion (sphincters int he stomach contracting to churn foood)
Performs chemical digestion (gastric juice)

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What is the structure and function of the gallbladder?

A small sac.

> Stores bile from the hepatic duct until needed by the small intestine.

> Concentrates bile by absorbing water.

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What is the structure and function of the duodenum?

The first and shortest section of the small intestine.

> Receives chyme from the stomach
Secretes mucous to neutralise the stomach acid in the chyme and prevent damage.
Mixes chyme with pancreatic juices and bile, breaking it down into monoamines.

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What is the structure and function of the jejunum?

The second part of the small intestine.

> Mixes chyme via peristalsis
Contains microvilli to increase contact between the cells in the jejunum (which are coated in enzymes) and the chyme.
Reabsorbs 90% of all nutrients.

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What is the structure and function of the ilium?

The last section of the small intestine.

> Absorbs B12, bile, salts and whatever else is not absorbed in the jejunum.
Contains millions of microvilli to increase surface area for reabsorption.

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What is the structure and function of the pancreas?

A gland posterior to the stomach. Has both endocrine and exocrine functions.

> Produces enzymes which converts fats and fatty acids to glycerol and digest polypeptides to smaller amino acids.
Produces acidic bicarbonate juice that neutralises acidic chyme in the small intestine.

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What is the structure and function of the large intestine?

AKA the colon, consists of:
>Cecum
>Ascending colon
>Transverse colon
>Descending colon
>Sigmoid colon

> Reabsorption of water and mineral ions - eg. Na and chloride
Formation and temporary storage of faeces
Contains bacteria which assist in vitamin production
Completes the bacterial fermentation of indigestible materials
Defecation

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What is the structure and function of the rectum/anal canal/anus?

> Usually empty until peristalsis pushes faeces into it.

>The anus is the terminal passage for faeces - has a sphincter which may be contracted to delay defecation.

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Name 4 tunics (layers) of the GIT and state the major function for each.

From outside to inside:

Tunica serosa - protection
Tunica muscularis - propels chyme through the digestive tract.
Tunica submucosa - provides nervous control to the mucosa.
Tunica mucosa - secretion, absorption & hormone production.

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Name the major hormones that control digestion

> Gastrin

> Secretin

> Cholecystokinin

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Name the major digestive enzymes

Saliva:
>Salivary amylase
>Lingual lipase

Gastric juice:
>Pepsin
>Gastric lipase

Pancreatic juice:
>Pancreatic amylase
>Pancreatic lipase
>Trypsin
>Elastase 
>Chymotrypsin

Microvilli:
>Maltase
>Sucrase
>Lactase

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Describe where chemical digestion takes place, what enzyme is involved and the optimum pH for the enzyme in the breakdown of carbohydrates.

> Oral cavity
Salivary amylase
6-7pH

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Describe where chemical digestion takes place, what enzyme is involved and the optimum pH for the enzyme in the breakdown of proteins.

> Stomach
Pepsin
1.5pH

> Duodenum
Trypsin, elastase & chymotrypsin
7-8pH

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Describe where chemical digestion takes place, what enzyme is involved and the optimum pH for the enzyme in the breakdown of fats.

> Oral cavity
Lingual lipase
4.5pH

> Small intestine
Lipase
7.0pH

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Define deglutition

The action or process of swallowing.

Explain the process of deglutition

The tongue shapes the chewed, lubricated bolus and moves it to the back of the oral cavity.
The tongue rises against the palate and closes the nasopharynx.
The uvula and palate seal off the nasal cavity.
The epiglottis covers the larynx.
Breathing is temporarily interrupted as the bolus travels down the oesophagus.

What is absorbed from the stomach?

> Water

> Alcohol

> Aspirin

What impact would the removal of the stomach or small intestine have on digestion? could food still be processed?

Stomach:
The digestive tract could still absorb food but since it acts as a reservoir for food, patients may experience gastric dumping if undigested food is moving through the digestive tract causing pain, diarrhoea & a drop in BGL. Absorption of B12 would be significantly impaired.

Small intestine:
If you remove part of the small intestine, you reduce the SA for absorption of fats, vitamins, proteins and carbs. there would be a significant risk of dietary deficiencies developing.

Explain the difference between and endocrine and exocrine gland.

Endocrine:
Release hormones - like insulin and glucagon - for the internal messaging system.

Exocrine:
Relates to releasing a substance through a duct - like enzymes.

What are the exocrine products secreted from the pancreas to the small intestine?

>Trypsin and chymotrypsin
>Pancreatic lipase
>Amylase
>Bicarbonate
>Water

> Other digestive enzymes

How does pancreatic juice affect the digestion of nutrients?

>Pancreatic juice helps to protect and prevent erosion of the intestinal mucosa - contains bicarbonate to help neutralise acidic liquid coming from the stomach. >Pancreatic juice contains digestive enzymes which break down protein, fat and starch.

What is the function of bile?

Bile has 2 important functions: 1. Contains bile acids which are critical for digestion and absorption of fats and fat-soluble vitamins in the small intestine. 2. Bile contains waste products which are eliminated from the body via secretion into bile and elimination in faeces.

Where is bile stored?

>Gallbladder - stores about 35-50mL of concentrated bile.

What is bile made of?

>Water >Electrolytes >Organic molecules such as bile acids, cholesterol, phospholipids and bilirubin

If a person's gallbladder is removed, what dietary restrictions might be necessary?

Most people who have had their gallbladder removed can maintain their previous diet. 2/10 people will experience diarrhoea after surgery which should improve in time. ``` Patients with ongoing diarrhoea may need to: >Reduce dietary fat >Increase high fibre foods >Avoid dairy and spicy food >Avoid drinks containing caffeine. ```

Describe what would happen to the detoxification process if liver function was impaired?

>Detoxification decreases or ceases >This results in a buildup of toxins like alcohol and drugs and changes to the properties of drugs can lead to overdose. >Increase in ammonia could result in brain injury.

What functions of the liver might be affected by excessive alcohol intake?

CIRRHOSIS!! >Jaundice from bilirubin not being conjugated >Bleeding disorders as no clotting factors would be made. >Increase in amino acids because they can't be converted to urea >No storage site for carbs >Albumin wouldn't be made so colloid osmotic pressure would not be maintained leading to oedema. >Hepatic encephalopathy >Problems with metabolism

Name the 3 subdivisions of the small intestine.

>Duodenum >Jejunum >Illium

Describe the features of the small intestine that allow nutrient absorption.

>Villi and microvilli which increase the SA of the small intestine. >Intestinal length >Plicae circulares - the folds in the small intestine that also increase SA.

What is the role of intestinal juice and brush border enzymes?

Intestinal juice: Provides a vehicle for absorption of substances from chyme as they come in contact with the villi. Brush border enzymes: Found of the surfaces of microvilli, break down food products.

Which regions of the gastrointestinal system does the duodenum receive substances from to facilitate the digestion of nutrients?

>The common bile duct - bile >Pancreatic duct - pancreatic enzymes >Stomach - processed food

What substances are absorbed in the large intestine?

>Water | >Mineral ions - Na, Fe, Ca and chloride

Why does a person experiencing diarrhoea have watery stools?

>Inflammation of the digestive tract especially the large intestine reduces water reabsorption as contents move rapidly through the digestive tract. >Inflammation also increases the amount of fluid in the region.

Why does a person experiencing constipation have hard stools?

Faecal matter sits in the large intestine and more and more water is reabsorbed, hardening the stool.

Describe the defecation reflex

1. Rectal wall distends 2. Stretch receptors send sensory nerve impulses to the sacral spinal chord 3. Motor impulses travel back to the descending colon, sigmoid colon, rectum and anus 4. Longitudinal rectal muscles contract and the internal anal sphincter opens. 5. If the external anal sphincter is voluntarily relaxed, defecation occurs and the faeces is expelled.

Define catabolism

The process by which metabolic pathways break down molecules into smaller units and release energy. ie. Polysaccharides into monosaccharides ie. Lipids into fatty acids ie. Proteins into amino acids

Define anabolism

The set of metabolic pathways that construct molecules from smaller units. eg. The construction of a protein from amino acids.

In anaerobic respiration, what substance is the end product of cellular metabolism?

Anaerobic respiration has 2 steps: 1. Glycolysis 2. Fermentation The end product of glycolysis is lactic acid.

Discuss any 5 reasons for vomiting.

>Food poisoning >Pregnancy >CNS disorders - meningitis, tumor >CVS disorders - MI, cardiac failure and hypoxia >Drugs >Excess alcohol >Spicy food >Stress/fear >Seeing someone else vomit

Describe the vomiting reflex

1. Taking a deep breath 2. Closing the airways 3. Contracting the diaphragm and abdominal muscles 4. Relaxing the gastroeosophageal sphincter

What happens to a person who has no food source?

>Metabolism slows down to conserve energy >Muscle mass is broken down for energy to conserve fat stores and keep the vital organs functioning. >People who are starving are likely to become ill and eventually die.

How long can a person survive without food as long as they drink water?

25-30 days.

What happens to a person who is NBM?

>Body releases available glucose >Body then breaks down fats and protein for energy