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Biology > 6: Human physiology > Flashcards

6: Human physiology Flashcards

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1
Q

What is peristalsis?

A

A wave of contraction and relaxation of the longitudinal and circular muscles of the alimentary canal, by which the contents are forced along the tube.

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2
Q

How do the longitudinal muscles and circular muscles work?

A

Antagonistically

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3
Q

Explain why digestion of large food molecules is essential.

A
  • Many molecules are too large to be absorbed by the villi

- Large food molecules are broken down so they can be reorganised

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4
Q

Discuss the roles of the enzymes secreted by the pancreas during digestion.

A
  • amylase breaks down starch to maltose
  • lipase breaks down fats to fatty acids and glycerol
  • Proteases break down proteins into smaller polypeptides
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5
Q

Describe the digestion of food in the human digestive system.

A
  • Chewing food makes smaller particles of food
  • Starch digestion begins in the mouth
  • Digestion of proteins in the stomach
  • Acid condition in stomach provides optimum pH for enzymes
  • Stomach muscle contraction causes mechanical digestion
  • Duodenum neutralises pH
  • Enzymes in small intestine complete digestion
  • Alkaline condition in small intestine provides optimum pH for enzymes
  • Bile salts help to emulsify fats
  • Amylase breaks down starch to maltose
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6
Q

Which enzymes does the pancreas secrete into the small intestine?

A

amylase, lipase and protease

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7
Q

How can the small intestine be divided?

A
  • Serosa (outer layer)
  • Longitudinal muscles
  • Circular muscles
  • Submucosa (connective tissue that has large veins and arteries)
  • Mucosa (innermost layer)
  • Mucosa consists of epithelium and villus
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8
Q

How are peptides digested?

A

Endopeptidases break proteins down into small peptides, then exopeptidases break the small piptides into amino acids, which are absorbed

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9
Q

Where does the absorption of food molecules take place?

A

In the small intestine, across the epithelium

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10
Q

How is the SA of the small intestine increased and why?

A

Villi, to ensure a large enough SA for transport proteins to absorb all necessary nutrients

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11
Q

What are the structures of a villi?

A

Outside to inside:

  • Goblet cells
  • Epithelium
  • Lamina propria
  • Capillary network
  • Nerve
  • Lacteal
  • Venule
  • Arteriole
  • Lymphatic vessel
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12
Q

What is absorption?

A

the taking in of digested food substances as well as minerals and vitamins from the lumen of the small intestine into the blood.

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13
Q

Explain how the structure of the villus is adapted for absorption.

A
  • Shape of villus has large SA to improve absorption
  • Thin walls allow fast diffusion
  • Capillaries to absord digested food products
  • Lacteal in villus to absorb fatty acids
  • Protein pumps in membrane to carry on active transport
  • large number of mitochondria provide ATP for active transport
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14
Q

Explain how the structure of the villus is adapted for absorption.

A
  • Shape of villus has large SA to improve absorption
  • Thin walls allow fast diffusion
  • Capillaries to absord digested food products
  • Lacteal in villus to absorb fatty acids
  • Protein pumps in membrane to carry on active transport
  • large number of mitochondria provide ATP for active transport
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15
Q

What is assimilation?

A

The use of molecules resulting from digestion. End products of digestion are distributed around the body through the circulatory system and are used by cells for anabolic processes or for respiration.

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16
Q

Two-step process of absorption

A
  • Substances to be absorbed move from the lumen into the epithelial villi
  • Amino acids and monosaccharides move from the villi into the capillaries and monoglycerides move into the lacteals
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17
Q

Methods of absorption

A

simple diffusion, facilitated diffusion, active transport, and pinocytosis

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18
Q

Simple diffusion (in terms of absorption)

A

Occurs when molecules are small and are hydrophobic (so they can pass through the phospholipid bilayers). This occurs mostly with the products of lipid digestion.

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19
Q

Facilitated diffusion (in terms of absorption)

A

Fructose, glucose and other hydrophilic monomers are moved by protein channels. Be aware, this still requires a concentration gradient.

20
Q

Active transport (in terms of absorption)

A

Is needed when the concentrations are lower in the lumen of the small intestine. Thus, the movement needs to occur against a concentration gradient. Glucose, amino acids and some mineral ions are transported in this way, which requires ATP. The cells of the epithelium have many mitochondria that can synthesise ATP for this process.

21
Q

Pinocytosis (in terms of absorption)

A

Draws in small droplets of liquid surrounded by a small section of the phospholipid membrane. This is most likely to occur with fat droplets in the lumen of the small intestine.

22
Q

How can the absorption of nutrients from the lumen of the small intestine be described?

A

Nutrients move from the lumen, across a plasma membrane into the epithelial cell, and across the plasma membrane again out of the epithelial cell and then into the capillary.

23
Q

How is starch broken down?

A
  • Begins with amylase in the saliva
  • Breaks down bonds in amylose and amylopectin
  • Still too large to pass through membranes
  • Immobilised enzymes in the epithelial cells of the small intestine break down the rest
  • Transported to the liver where it enters the general circulation
24
Q

What is dialysis?

A

the separation of smaller molecules from larger molecules in solution by selective diffusion through a partially permeable (also known as selectively permeable or semipermeable) membrane.

25
Q

In an iodine solution, when is starch present and when it is not?

A

Brown-orange: not present, black-blue: present

26
Q

What did Harvey propose about the circulatory system?

A
  • Arteries and veins were part of a single connected blood network
  • Arteries pumped blood from the heart
  • Veins returned blood to the heart
27
Q

What is the structure of the heart?

A

Four chambers, two atria and two ventricles

28
Q

What do the atria do?

A

Blood returning to the heart is collected via veins and passed on to ventricles

29
Q

What do the ventricles do?

A

Expel blood from the heart at high pressure via arteries

30
Q

What kind of blood does the left side of the heart pump?

A

Oxygenated, around the body (systemic circulation)

31
Q

What kind of blood does the right side of the heart pump?

A

Deoxygenated, to the lungs (pulmonary circulation)

32
Q

Which side of the heart is thicker?

A

Left side, must pump blood further

33
Q

What is an artery?

A

Vessel that pumps blood from the heart

34
Q

What is a vein?

A

Vessel that returns blood to the heart

35
Q

Structure of an artery

A
  • Narrow lumen
  • Thick wall
  • Arterial wall of an inner layer of muscle and elastic fibres
  • Endothelium
36
Q

Composition of the three layers of the arterial wall

A

Tunica intima, tunica media, tunica adventitia

37
Q

What is vascoconstriction?

A

when the circular muscles surrounding the arteries resist the outward pressure and constrict. occurs when the heart contracts (systolic blood pressure)

38
Q

What is vascodilation?

A

when the smooth muscles surrounding the arteries relax between heart beats (diastolic blood pressure)

39
Q

What is stroke volume?

A

the volume of blood pumped out of the left ventricle of the heart during each contraction (or heartbeat).

40
Q

What is cardiac output?

A

the volume of blood the heart pumps through the circulatory system in a minute.

41
Q

What are the purpose of valves?

A

To ensure that blood flows in one direction only

42
Q

How can veins ensure that blood flows back to the heart despite lower pressure?

A

Through the skeletal muscles next to the veins and the valves found inside veins. Blood flow in veins is helped by pressure exerted by skeletal muscles.

43
Q

How are arteries and veins connected?

A

By a capillary network

44
Q

Why must capillaries be formed?

A
  • The nutrients and oxygen in blood need to reach all cells in the body
  • Size and wall structure of arteries is too big for that purpose
  • Arteries cannot fit between individual cells if theyre large, and diffusion is not efficient if there are many cells through which substances must diffuse
  • arteries divide into arterioles and then into capillaries and then into venules and then into veins
  • capillaries are only one-cell thick
  • have permeable walls that allow for material exchange
45
Q

Capillary structure

A
  • small diameter
  • wall of single layer of cells
  • surrounded by basement membrane
  • pores
  • can be continuous, fenestrated or sinusodial
46
Q

What is tissue fluid?

A

Made of water, sugars, salts, fatty acids, amino acids, coenzymes and hormones, and waste products. Enhanced material exchange between tissue cells and fluid. Tissue fluid then reabsorbed into capillaries with CO2, water and waste.

47
Q

How does blood flow through the body?

A
  • Blood enters the heart into the right atrium of the heart, is deoxygenated from the body tissues
  • As the atrium contracts, blood flows from the right atrium into the right ventricle through the valve
  • When the ventricle is full, it begins to contract
  • The increased pressure of blood against the valve forces it shut
  • Prevents blood from flowing backwards into the atrium
  • As the ventricle contracts, blood leaves the heat through the pulmonary valve, into the pulmonary artery and flows to the lungs where it is oxygenated
  • the pulmonary vein carries oxygenated blood from the lungs into the left atrium of the heart
  • As the atrium contracts, blood flows from the left atrium into the left ventricle
  • when the ventricle is full, it begins to contract
  • increased pressure from blood forces valve shut
  • as the ventricle contracts, blood leaves the heart through the aortic valve, into the aorta and to the body.

Biology (3 decks)

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