The Heart & Organization of Blood Vessels

Question 1

Functions of the Cardiovascular System

Answer 1

• maintain homeostasis
• transport of:
  
  • metabolites and wastes
  • hormones and signal molecules
  • dissolved gasses
  • cells involved in immune and inflammatory responses
• regulation of body temperature

Question 2

Components of the Cardiovascular System

Answer 2

1. Pump - the heart
2. Conducting Vessels - arteries & veins
3. Sites for exchange with the tissues - capillaries
4. Drainage system for excess tissue fluids - lymphatic vessels

Question 3

Two Circuits of the Cardiovasc. System

Answer 3

1. Pulmonary circuit –> lungs

2. Systemic circuit –> rest of the body

Question 4

Is circulation in parallel or in series?

Answer 4

in parallel

Question 5

Atriums vs. Ventricles of the Heart

Answer 5

Atriums - pump base –> apex

Ventricles - pump apex –> base

Question 6

Location of the Heart

Answer 6

• resides in the mediastinum (middle of the sternum - region of the thorax between the lungs)
• contains the heart, esophagus, trachea, thymus gland, and large blood vessels

Question 7

Pericardium

Answer 7

• pericardial cavity is formed by the pericardial sac - contains the heart
  (inside) endocardium –> myocardium –> visceral peridcardium/epicardium) –> parietal pericardium

Question 8

Heart Vavles

Answer 8

occur between:
- atria & ventricles
- ventricles and outflow vessels (pulmonary artery & aorta)
valves ensure one-way flow of blood (open under pressure, close to prevent back flow)
- provide block between muscle of atria and muscle of ventricles

Question 9

Tricuspid Valve

Answer 9

R Atrium & R Ventricle

Question 10

Bicuspid (Mitral) Valve

Answer 10

L Atrium and L Ventricle

Question 11

Semilunar Valves

Answer 11

between ventricles and pulmonary artery/aorta

Question 12

Ventricular Diastole

Answer 12

relaxation

• bicuspid/tricuspid valves open
• semilunar valves closed

Question 13

Ventricular Systole

Answer 13

contraction

• bicuspid/tricuspid valves closed
• semilunar valves open
• pressure in ventricles > pressure in arteries

Question 14

Cardiac Muscle

Answer 14

• single nucleus
• join end:end
• branches (Y) –> depolarization passes as a wave
• ionic coupling by gap junctions

Question 15

Conduction System

Answer 15

1. Sinoatrial node
2. Atrioventricular node
3. Bundle of His
4. Right & Left Bundle Branches
5. Purkinje Fibres

Question 16

Cardiac Cycle

Answer 16

• all the events associated with one heart beat
• two atria contract while the ventricles relax = atrial systole, ventricular diastole
• two ventricles contract while the atria relax = ventricular systole, atrial diastole

Question 17

Layers of Vessel Wall (3)

Answer 17

1. Tunica interna
2. Tunica media
3. Tunica externa

Question 18

Tunica interna

Answer 18

internal layer of blood vessel walls

- composed of simple squamous epithelium (endothelium) & thin layer of connective tissue (serous membrane)

Question 19

Tunica media

Answer 19

middle layer of blood vessel walls

• thickest layer
• composed of elastic fibres (for recoil) & smooth muscle (regulates diameter of vessel)

Question 20

Tunica externa

Answer 20

outer layer of blood vessel walls

• composed of connective tissue
• attaches vessel to surrounding connective tissue

Question 21

Types of Vessels

Answer 21

Closest to Heart:
- large vein
- elastic artery
Medium:
- medium-size vein
- muscular artery
Far from Heart:
- venule
- arteriole
closer to heart = decrease smooth muscle, increase elasticity

Question 22

Elastic (conducting) Arteries

Answer 22

• largest diameter arteries
• tunica media contains high density of elastic fibres
• stretch & recoil in response to pumping of heart
• even out pressure surges

Question 23

Muscular (distributing) Arteries

Answer 23

• medium-sized arteries
• distribute blood to skeletal muscles & internal organs
• tunica media contains predominantly smooth muscle
• able to vasoconstrict (close) & vasodilate (open)

Question 24

Arterioles

Answer 24

• small to microscopic vessels
• poorly defined tunica externa
• media composed of few smooth muscle cells
• deliver blood to capillaries
• change in luminal diameter regulates blood pressure (decrease diameter –> increase pressure)

Question 25

Capillaries

Answer 25

- smallest blood vessels - connect arterioles to venules - mediate exchange between blood and surrounding tissues - *just a tunica interna

Question 26

Types of Endothelial Cells

Answer 26

1. Continuous - connected by tight junctions 2. Fenestrated - can have diaphragm (appear continuous) or no diaphragm) 3. Discontinuous - complete gaps

Question 27

Continuous Vs. Fenestrated Capillaries

Answer 27

``` Continuous: - things cannot move between cell walls, must pass through cells = control over entry/exit - takes more time - tight junctions - eg. in brain Fenestrated: - sieve-like - allows material to pass through easily - faster - eg. in liver ```

Question 28

Control of Blood Flow in Capillary Bed

Answer 28

- precapillary sphincters control blood flow through capillary - metarterioles shunt blood through capillary bed when sphincters closed ie. cold day - contract precapillary sphincter --> stop blood flowing into capillaries (conserve heat) --> blood redirected through metarteriole shunt (blood has less time to interact with tissues)

Question 29

Veins

Answer 29

collect blood from organs & tissues & return it to heart

Question 30

Venules

Answer 30

- collect blood from capillaries | - wall composed primarily of tunica interna

Question 31

Medium & Large Veins

Answer 31

- tunica externa thickest layer

Question 32

Valves

Answer 32

in walls of veins - prevent backflow of blood | - venous compression caused by contraction of adjacent muscles aids in maintaining blood flow

Question 33

Fluid Loss to Tissues

Answer 33

- filtration from plasma to interstitial fluid (capillaries) - interstitial fluid flows from tissues back into lymphatic vessels - lymphatic vessel joins vein (lymph flow) --> back to heart

Question 34

Lymphatic Vessels

Answer 34

- lymphatic system extremely low pressure - vessels very thin - endothelial cells discontinuous

Question 35

Lymph Flow Vs. Blood Flow

Answer 35

- blood flow is actively pumped through vessels by heart - lymph flows passively along a pressure gradient - no pump

Question 36

Lymphatic Valves

Answer 36

- large number of valves | - prevent backflow of lymph