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Human Structure & Function > Digestive System > Flashcards

Digestive System Flashcards

1
Q

What are enzymes?

A

A protein catalyst that increases the rate at which a chemical reaction proceeds. They are highly specific (active site).

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2
Q

What enzyme breaks down lipids?

A

Lipase

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3
Q

What enzyme breaks down proteins?

A

Protease.

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4
Q

What enzyme breaks down carbohydrates?

A

Amylase

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5
Q

What are the salivary glands?

A

Glands that produce and secrete saliva into the oral cavity.

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6
Q

What is the role of saliva?

A

Protects oral cavity, moistens, lubricates and digests food.

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7
Q

What is lysozyme?

A

An antibacterial enzyme found in the mouth

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8
Q

What is the process of swallowing?

A
  1. Voluntary phase: tongue pushes bolus to the back of the oral cavity towards the pharynx.
  2. Pharyngeal phase: soft palate closes off nasopharynx. Bolus touches receptors on oropharynx and swallowing reflex moves bolus down pharynx and into oesophagus. Epiglottis covers trachea.
  3. Oesophageal phases: bolus moves down oesophagus by peristalsis.
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9
Q

What is the role of the stomach?

A

Stomach churns bolus into chyme (thick liquid).

Produces mucus, hydrochloric acids and protein-digesting enzymes (pepsin).

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10
Q

What is the structure of the stomach?

A

Contains a thick mucus layer that lubricates and protects epithelial cells on stomach wall from acid (pH: 2-3).
Opening: gastroesophageal (to oesophagus) and pyloric sphincter (to duodenum).

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11
Q

What are the layers of the stomach?

A

Visceral peritoneum, muscularis (outer longitudinal, middle circular, inner oblique), submucosa, mucosa and rugae (folds in stomach wall that allow stomach to stretch after eating).

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12
Q

What are the movements of the stomach?

A

3 muscles layers enable churning of food to make chyme.
Combination of mixing waves (80%) and peristaltic waves (20%).
Both esophageal and pyloric sphincters are closed.
Stomach empties ever 4 hours (6-8 after a fatty meal).

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13
Q

What is the structure of the small intestine?

A

~6m in length, small diameter.
Large surface area for absorption.
Divisions: duodenum (first 25cm), jejunum (2.5m), ileum (3.5m).

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14
Q

What is the role of the duodenum?

A

Chyme mixes with various digestive enzymes.
Bile enters from liver/gall bladder via the common bile duct, emulsifies fats.
Enzymes enter via pancreatic duct.
Lipase: breaks down lipids
Pancreatic amylase: breaks down carbohydrates.
Trypsin: breaks down proteins.

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15
Q

What is the structure of the wall of the small intestine?

A

Folds increase surface area.

  1. Plicae circulares - circular folds in the wall.
  2. Villi - folds of mucosa that contain capillaries and lacteals.
  3. Microvilli - small folds on the epithelial cell surface.
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16
Q

Where do nutrients that are absorbed in the small intestine travel to?

A

Lipids travel to the lacteals and lymph nodes.

Carbohydrates and proteins travel to the capillaries and the blood.

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17
Q

What is the role of the liver in the digestive system?

A

Produces bile (~100mL/day). Stores glucose (as glycogen) and lipids for energy. Involved in detoxification.

18
Q

What is the role of the gallbladder in digestion?

A

Stores concentrated bile.

19
Q

What is the role of the pancreas in digestion?

A

Produces digestive enzymes. Produces insulin and glucagon for blood sugar homeostasis.

20
Q

What is the role of the large intestine?

A

Absorption of water.
Bacteria/microbes synthesise vitamin B & K.
Defecation reflex.

21
Q

What does the large intestine do in digestion?

A

1500mL of chyme enters the cecum, 90% absorbed yielding 80-150mL of faeces.
Transit time: 18-24hrs (chyme to faeces).

22
Q

What is the structure of the large intestine?

A

Extends from ileocecal junction to anus.

Consists of cecum, colon (ascending, transverse and descending, sigmoid), rectum and anal canal.

23
Q

Summarise the digestive process.

A
  1. Breakdown of food molecules by mechanical and chemical digestion in mouth and stomach.
  2. Absorption of nutrients in small intestine, absorption of water in large intestine.
24
Q

What are nutrients?

A

Chemicals taken into the body to produce energy and provide building blocks to build other molecules.

25
Q

What are the six classes of nutrients?

A

Carbs, proteins, lipids, vitamins, minerals and water.

They are all organic molecules which means they all contain carbon.

26
Q

What are some examples of carbohydrates?

A

Mono/di/polysaccharides - plants/vegetables.

27
Q

What are some examples of lipids?

A

Triglycerides - oils. dairy, animal fat, eggs.

28
Q

What are some examples of proteins?

A

Chains of amino acids - meat, fish, poultry.

29
Q

What is the structure of carbohydrates?

A

Contain carbon, hydrogen and oxygen.
2 hydrogen for every carbon.
Can be mono, di or polysaccharides.

30
Q

What is the process of carbohydrate absorption?

A

Polysaccharide chain digested by saliva in the mouth and pancreatic amylase in the duodenum.
Disaccharide chain digested by sucrase in the intenstine
Monosaccharide chain - glucose absorbed into blood via villi/microvilli in intestine, transported to liver via hepatic portal vein.

31
Q

What are some examples of mono, di and polysaccharide carbohydrates?

A

Monosaccharides: fructose, glucose, galactose.
Disaccharides: sucrose, lactose, maltose.
Polysaccharides: glycogen, starch and cellulose.

32
Q

What are the uses of carbohydrates in the body?

A

Glucose produces ATP. Excess glucose is turned into glycogen and stored in muscle and liver cells. Excess beyond storage becomes fat. Sugars also become part of DNA, RNA, ATP, glycoproteins and glycolipids.

33
Q

What is the structure of proteins?

A

Contains carbon, hydrogen, oxygen, nitrogen and sometimes sulfur. Building block: amino acids. Each amino acid has an amine group (NH2), a carboxyl group (COOH), a hydrogen group and a side group.

34
Q

What are the functions of proteins?

A

Globular proteins form haemoglobin. Form muscle proteins or connective tissue. Assist in cell membrane transport. Assist in enzyme formation, hormones and antibodies.

35
Q

What is the process of protein absorption?

A

Protein digested by pepsin in the stomach. Polypeptides digested by trypsin in the duodenum. Peptides and individual amino acids are absorbed into the blood.

36
Q

What is the structure of lipids?

A

Composed of carbon, hydrogen, oxygen and sometimes nitrogen and phosphorus.

37
Q

What is the function of lipids?

A

Lipids/fats are broken down to release energy.

38
Q

What is the structure of triglycerides?

A

Glycerol + 3 fatty acids. Triglycerides make up 95% of the body.

39
Q

What are the types of fatty acids?

A

Saturation: refers to how many H atoms on each chain.
Saturated: animal fats.
Unsaturated: contains one or more double bonds in the carbon chain, less H.
Trans fats: unsaturated fats artificially altered to be more saturated.

40
Q

What is the process of lipid absorption?

A

Begins in duodenum, bile from gall bladder emulsifies lipids.
Lipase from pancreas causes a further breakdown.
Short chain fatty acids are absorbed into lympthatic system.
Lipids are stored in adipose tissue and liver.

41
Q

What are the uses of lipids in the body?

A

Cholesterol: component of plasma membrane.
Phospholipids: plasma membranes, myelin sheath, bile.
Eicosanoids: inflammation, blood clotting, tissue repair, smooth muscle contraction.

Human Structure & Function (8 decks)

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