Cardiology basics

Question 1

Need for a heart

Answer 1

Oxygen and nutrients
Diffusion distance only sufficient for small animals
Diffusion distance is too large for large animals
Cannot supply all tissues with substances they require
Too slow

Question 2

Einstein’s equation

Answer 2

Time is proportional to diffusion distance squared

Question 3

Thrombus

Answer 3

Blood clot forms in vessels and blocks delivery of blood to the tissue > ischaemia (restriction of blood flow) > tissue hypoxia > necrosis > arrhythmia > heart attack

Question 4

Role of circulation

Answer 4

Overcome diffusion which would be too slow for central cells
Bulk flow followed by diffusion

Question 5

Open circulatory

Answer 5

Low pressure
Haemocoael is the body cavity and haemolymph is the fluid
There is
Little control

Question 6

Closed circulation

Answer 6

Vessels means higher pressure
More control is possible and required
Veins carry blood to the heart and the arteries pump from the heart
Separation of oxygenated and deoxygenated blood

Question 7

Single system

Answer 7

Blood flows around the body once per circuit, seen in fish where blood flows from the heart to the gills for gas exchange then to the rest of the body then to the heart

Question 8

Double system

Answer 8

Blood flows from the heart to the lungs for gas exchange then back to the heart to be repressurised before flowing to the rest of the body

Question 9

Arrangement of the circulation

Answer 9

Aorta - artery which carries blood from the heart to the systematic circulation. The arteries branch into smaller arterioles which then pass into capillaries
Capillaries - thin walls for nutrient exchange and waste disposal in opposing directions
Blood flows in venues and then veins which lead back to the heart via the inferior and superior vena cava

Question 10

Aorta

Answer 10

Aorta has thick collagen to withstand and maintain high pressure
Ascending aorta - from the heart
Descending aorta - part of aorta that runs down the chest and abdomen splitting into 2 arteries

Question 11

Valves and Annulus Fibrosus

Answer 11

ANNULUS FIBROSUS holds cardiac valves (AV/SL)
AV valves = thin flaps of connective tissue which are joined at the base of connective ring, flaps connect to the CHORDAE TENDINAE which are attached to PAPILLARY MUSCLES to stabilise the chordae
The chordae support the closing of the AV valve to prevent it being pushed back into the atrium

Question 12

AV valve

Answer 12

Right = tricuspid 
Left = mitral (bicuspid)

Question 13

SL valve

Answer 13

Aortic aneurysms pulmonary valves

Both have 3 cusps and due to their shape do not have chordae tendinae

Question 14

Heart wall layers

Answer 14

Endocardium is a thin sheet of flattened endothelial cells over connective tissue inside the heart
Myocardium is the cardiomyocytes which form middle layer of wall itself
Epicardium is the thin layer of connective tissue covering the heart
Pericardium = entire heart enclosed in pericardial sac and space between epi and peri are filled by pericardial fluid

Question 15

Tunica intima

Answer 15

Thin layer of endothelial cells and elastic connective tissue

Question 16

Tunica media

Answer 16

Smooth muscle and bands of elastic fibres
Varies in thickness depending on function of the blood vessel
Large arteries have thick media to expand and recoil to smooth pressure changes

Question 17

Tunica adventitia

Answer 17

Collagenous extracellular matrix containing fibroblasts, nerves, and blood vessels
In the limb, contains pain nerve receptors

Question 18

Vasa vasorum

Answer 18

Supplies thick media

Question 19

Capillaries

Answer 19

Consists of just single layer of endothelial cells

Question 20

Venules and veins

Answer 20

Thin walls and valves to prevent back flow
They have large cross sectional area thus decreased resistance
Large store of blood
Veins aid venous return to maintain cardiac output

Question 21

Fetal hb

Answer 21

Dependent on placenta rather than pulmonary ventilation
Fetal hb can bind greater concentrations of oxygen and also release this oxygen to fetal tissues at lower oxygen tensions than adult hb
Material hb has a lower affinity for oxygen than fetal hb as shown by P50 which is where 50% p(o2) is saturated, fetal hb curve shifted to the left

Question 22

Fetal shunts

Answer 22

Foramen ovale - allows blood to shunt between the LA and RA which bypasses the pulmonary circulation
Upon first breath there is a large increase in pulmonary blood flow lowering the RA pressure and increasing LA pressure > septum closed the foramen ovale

Ductus arteriosus shunts blood that manages to enter the pulmonary artery into the aorta

Ductus venosus shunts richly oxygenated blood to the heart and bypasses the liver circulation as nutrition is not via the GI tract

Question 23

Ductus shunts after birth

Answer 23

Ductus shunts are responsive to vasodilator prostaglandins secreted by the placenta however after birth there is no umbilical cord supply so they close after birth
Ductus arteriosus > ligamentum arteriosum
Ductus venosus > ligamentum venosum