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Human Physiology > The Digestive System > Flashcards

The Digestive System Flashcards

1
Q

Name the 3 functions of the GI tract

A

Mechanical Digestion and motility

Secretion and chemical digestion

Absorption and defecation

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2
Q

Name 5 things involved in mechanical digestion

A

Chewing

Swallowing

Churning

Mixing

Propelling

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3
Q

Explain the process of Mastication

A

Mechanical food begins in the mouth

Mastication - the chewing of food uses the teeth and tongue

A single bite can be a voluntary process but general chewing is an involuntary pattern of movement regulated by the brain stem

Mechanoreceptors in the teeth and tongue provide information about the food

The product is a soft warm mush mixed with amylase called a bolus

When mastication is complete the swallowing reflex occurs

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4
Q

In what types of people can the ability to chew food be lost in

A

Patients with brain injury or degenerative disorders

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5
Q

Explain the process of the swallowing reflex

A

Reflex action and involves:

Closure of the epiglottis

Opening of upper oesophageal sphincter

Process failure results in choking or pulmonary aspiration

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6
Q

Explain what dysphagia is

A

Lack of or impaired ability to swallow

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7
Q

Explain symptoms of dysphagia

A

Difficulty swallowing

Bringing food back up or feeling that food is stuck

Inability to swallow saliva resulting in drooling

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8
Q

Explain the causes of dysphagia

A

Any condition that affects the nervous system, such as a stroke, head injury, or dementia

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9
Q

Explain treatment for dysphagia

A

Depending on the cause can be overcome with an operation or therapy, sometimes food needs to be given processed or through a tube

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10
Q

What is the long-term effect of leaving dysphagia untreated?

A

Malnutrition

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11
Q

Explain how the basic propulsion of food works

A

Peristaltic contraction

Moves food along the gut in an oral-to-anal direction

Orchestrated waves of contraction and relaxation that move “wave-like” along segments of the gut

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12
Q

Explain the role of the oesophagus in digestion

A

The bolus moves from the throat into the esophagus

Moves along by rhythmic peristalsis one directional wave of muscle contraction

The primary peristaltic wave forces the bolus down the oesophagus and into the stomach in a wave lasting about 8-9 seconds

If the food gets stuck stretch receptors in the oesophageal lining stimulate a reflex response, a second wave that continues to force the food down

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13
Q

Explain the role of the stomach in the process of digestion

A

The stomach secretes about 2 liters of gastric juice each day

Peristalsis contractions continue in the stomach with the addition of a churning motion provided by the oblique layer

Churning action if the stomach with the digestive juices physically breaks down food

The stomach controls the release of the product water chime into the small intestine

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14
Q

What are the symptoms of gastric reflux?

A

Heartburn pain

Acid reflux

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15
Q

Explain the causes of gastric reflux

A

Excessive alcohol

Being overweight or pregnant

Eating a high-fat diet

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16
Q

Explain the long-term effects of gastric reflux

A

Ulcers

Barretts Oesophagus

Oesophageal Cancer

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17
Q

Explain treatments for gastric reflux

A

Antacids

Alginates

H2 receptor antagonists

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18
Q

How do you feel full?

A

Nerve stretch receptors signal to the brain

Ghrelin stops being released

If you have had a bariatric surgery

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19
Q

Explain the role of small intestine segmentation contractions in the process of digestion

A

Initially, peristalsis propels the food

Period segmentation disperses the
food over the bowel surface

The muscular mucosae have an independent
regular contractions.

Gastrin from the stomach stimulates
Motility

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20
Q

Explain what haustration n in the colon is and how it is part of digestion

A

The haustra (round part of the large intestine) contracts twice an hour

The haustrum distends as it fills with chime

Its eventually stimulated to contract this pushes the contents to the next haustrum

Peristalsis contractions in the colon 2-4 times a day

This is the longest part of the digestive process

this forms the liquid food slowly into a solid mass

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21
Q

Name the 3 motility behaviors that affect the smooth muscle layer in the GI tract

A

Peristalsis Contractions

Segmentation Conractions

SlowWaves (Basic Electrical Rhythm)

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22
Q

Explain the role of the enteric nervous system in the GI tract

A

Located solely in the GI tissue within the: myenteric plexus (controls motility), Submucosal plexus (controls secretory functions)

Runs the whole length of the gut and contains approximately 100 million neurons

functions independently of the CNS and sends information directly to smooth muscle, secretory cells, endocrine cells, and GI blood vessels

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23
Q

What does digestion break carbohydrates (starch and sugars), Proteins, and fats into

A

Carbohydrates to glucose

Proteins to amino acids

Fats to fatty acid and glycerol

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24
Q

Explain the process of salivation

A

Saliva lines the oral cavity providing protection and hydration it increases the sight, smell, or taste of food.

Saliva has antimicrobial components such as lysozyme and agglutins to aggregate bacteria to assist clearance

It detects dehydration and informs the conscious brain to drink

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25
Q

When do salivary glands secrete?

A

In response to parasympathetic activity, induced by physical, chemical, or psychological stimuli

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26
Q

Explain the role of accessory glands in the oral mucosa

A

Secrete continuously under enteric control

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27
Q

Explain the process of lactose digestion

A

Lactose is a disaccharide which comes from milk and milk products
It is digested by lactase into glucose and galactose

28
Q

Explain what happens if is lactose intolerant

A

Lose the ability to produce lactase

Usually as a teenager or adult

Lactose remains undigested in the bowel

Bacteria feed on the lactose-produced waste gases and chemicals

Bloating, gas, and diarrhea

29
Q

Why is fiber in the diet important?

A

Gives structure to the food bolus holding water in the bowel and easing transit

30
Q

What happens if a person has a low-fiber diet and a high-fiber diet

A

Low fiber diet

Constipation

Indicated in a higher incidence of bowel cancer

High fiber diet

Helps maintain weight

Helps reduce diabetes

Helps reduce cholesterol levels

31
Q

Where does protein digestion start?

A

Stomach

32
Q

Where are bile and pancreatic juices released?

A

Duodenum

33
Q

Name the 3 components of digestive enzymes

A

Digestive enzymes - Lipase, Amylase, Nuclease, Typrsinogens, Chymotrypsinogen

Buffer - HCO3- - Neutralises acidic chyme entering from the stomach

Non-pancreatic secretion - Mucus secretion by goblet cells in GI to protect the gut wall from acidic chyme and self-digestion

34
Q

Name the enzyme that activates enzymes in the pancreatic juice

A

Enterokinase

35
Q

Why is enterokinase an important enzyme in pancreatic juice

A

Brush border enzyme

Directly or indirectly activates three digestive enzymes secreted in pancreatic juice

36
Q

Explain the cause of coeliac disease and what happens to a person who has this disease

A

Is caused by a protein of wheat, rye, and barley called GLUTEN

Immune response is generated to the Gliadin

Inflammation destroys the delicate surface of the bowel

Common disorders often untreated, inherited element

37
Q

Name the 2 components that make gluten

A

Gliadin

Glutenin

38
Q

Explain how the bowel of a person who has coeliac disease is different from a healthy individual

A

Reduced ability to digest and absorb food

Deficiency in iron, folate B12, and iron

Issues during pregnancy

Increased risk of bowel cancer

39
Q

Explain what cholestasis is, its cause, symptoms, and treatment

A

A condition caused when a person’s bile cannot pass from the liver to the duodenum

Causes:

Blockage of the liver or gallbladder

Drug reaction, hepatitis, or fibrosis

Pregnancy

Malignancy

Symptoms:

Pruritus (itchiness) from the elevated bile serum

Obstruction - jaundice, pale stool, and dark urine

Treatment:

Depending on the cause, remove the blockage or treat other symptoms

40
Q

Explain what is digestion

A

Digestion is the breakdown of foods into molecules.

41
Q

Where does digestion start/ where does most digestion occur?

A

Start: Mouth

Most digestion occurs in the duodenum and jejunum (small bowel)

42
Q

What type/how much absorption occurs in the stomach?

A

A very small amount of absorption occurs in the stomach.

Medication such as aspirin and non-steroid anti-inflammatory

Alcohol

Caffeine

43
Q

Is the lining of the stomach designed for absorption or not?

A

The lining of the stomach is not designed for absorption as many of the chemicals irritate the lining of the stomach

44
Q

Explain the role of the small intestine in the absorption

A

The Intestinal lining increases absorption because of:

Vili - finger-like extensions in the small intestine

Microbilli - present on the apical surface of intestinal epithelial cells. Microvilli cate the brush border

45
Q

After how many days does gut epithelium renew

A

Every 3-5 days

46
Q

Explain the absorption of proteins

A

Free amino acids are carried via the Na+-dependent transporters

Di and tripeptides are carried via H+-dependent transporters

Larger peptides transport via transcytosis

47
Q

Name the Fat-soluble Vitamins

A

Vitamin A

Vitamin D

Vitamin E

Vitamin K

48
Q

How do fast soluble vitamins get digested?

A

Absorbed with the droplets and move through the system with the chylomicrons

49
Q

What happens if a person overdoses on the following vitamins: Vitamin A and Vitamin D

A

Vitamin A - Decreases bone density, which is dangerous during pregnancy

Vitamin D - Ca+ increases build-up in kidneys and loss from bones

50
Q

Name and explain how water-soluble vitamins are digested

A

Vitamins B1-9, B12 and Vitamin C

The body does not store water-soluble vitamins they are removed with urination

Vitamin B1-9 and Vitamin C are absorbed by mediated transport (i.e. require cotransporters such as Na+)

B12 is used in cellular metabolism and is necessary for the production of red blood cells. The parietal cells produce intrinsic factor, which is necessary for the absorption of vitamin B12

51
Q

Explain how the minerals Na+, K+ and Ca+ are absorbed

A

Na+ is actively transported across the small intestine epithelium using transporters similar to those in the kidney

K+ is passively absorbed in the small intestine (but depends on electrochemical gradients)

Ca+ is paracellular absorption according to gradients, transcellular in the small intestine when levels are low by carrier proteins synthesised from Vitamin D

52
Q

How many mg of iron do enterocytes add to plasma through the absorption of dietary iron?

A

1-2 mg

53
Q

Explain the process of iron absorption

A

Occurs in the enterocytes (brush border cells) of the proximal duodenum

Dietary iron occurs in these major forms

Ferrous ion (Fe2+)

Ferric Iron (Fe3+)

Haem iron (Fe2+) chelated into a complex organic compound to complete the haem structure, which occurs in hemoglobin, myoglobin, and certain enzymes

Ferriductase

Transmembrane enzymes catalyse the reduction of Fe3+ to Fe2+

Divalent metal transports 1 DMT 1 membrane transporter transfers the Fe 2+ inside the intestine enterocyte

54
Q

Explain the absorption of water and minerals

A

9L of fluid enters the lumen of the gut per day

7.5L is reabsorbed from the small intestine

Absorption of organic nutrients occurs in the small intestine (duodenum and jejunum). This creates an osmotic gradient for water absorption

Dietary fibre

55
Q

Name and briefly explain the 3 nutrient routes

A

Hepatic portal system - carries nutrients to the liver

Lymphatic system - for fats

Enterohepatic circulation - recycles bile salts

56
Q

Explain the role of the hepatic portal system in absorption

A

Absorbed nutrients enter the hepatic portal circulation and are transported to the liver

57
Q

Why is it important for the enterohepatic circulation to recycle bile?

A

This recirculation is important in maintaining fat digestion. In a single meal, bile salts will be recycled from2-5 times

58
Q

Name the 7 regions of the large intestine

A

Caecum

Ascending Colon

Descending Colon

Transverse Colon

Sigmoid Colon

Rectum

Anus

59
Q

Name the main functions of the large intestine

A

Uptake of water

Bacterial activity (produces Vitamin K and B12)

Storage

Haustration: slowing down of propulsion

Peristalsis 2-4 times per day

60
Q

What factors are transit times affected by

A

Diet

Stress

Congenital Abnormality

Pathogens

61
Q

Explain the role of the rectum in the absorption

A

Storage of feces

The presence of feces stimulates the elimination

Muscle contraction

Anal sphincters - voluntary control, opens for elimination

62
Q

Explain how the GI tract is regulated through the cephalic phase

A

Sight, smell, or food in the mouth is detected by the brain, and via the medulla oblongata the cranial nerves stimulate salivary glands and the Vagus nerve stimulates the secretion of gastrin in the stomach

63
Q

Explain the gastric phase

A

Stimulated by the distension of the stomach - further secretion of gastrin therefore gastric juices and motility. This phase can be fast feedback from the enteric nervous system or slow feedback via the parasympathetic system and vagus nerve

64
Q

Explain the intestinal phase

A

Stimulus chime entering the intestine and nervous and hormonal control stop the gastric secretions. The gastrin remains in the chime and continues to have actions

65
Q

Give the primary purpose of the GI tract

A

Extract nutrients from ingested food (digestion) and deliver them to the bloodstream for distribution to cells in the body (absorption)

66
Q

By regulating the Gi functions what does the maximize?

A

Efficiency of digestion and absorption

Human Physiology (9 decks)

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