2. Gross + Cellular structure of the heart

Question 1

Synopsis

Answer 1

Role of the heart

Gross structure of the heart

Heart valves location and role

Cellular structure-function of cardiac muscle

Question 2

Major Roles

Answer 2

Cardiac muscle is specialised form of striated muscle -> myocardium (heart muscle)

2 major roles:

• > supply oxygenated blood containing nutrients to major organs
• > remove waste products formed during metabolism (via lungs + kidneys)

Circulation divided into 3 separate parallel circuits

• > pulmonary (lungs)
• > coronary (heart)
• > systemic (rest of body)

Question 3

SUMMARY

Answer 3

-> heart has 4 chambers - 2 atria + 2 ventricles
-> pulmonary, coronary + systemic circulations arranged in parallel
-> Left ventricular wall thicker than right ventricle (due to chamber pressure)
the pericardium protects the heart, whereas pericardial serous fluid lubricates heart to reduce friction
-> Uni-directional blood flow due to one-way heart valves that open + close depending on pressure gradients
-> Papillary muscles stop A-V valves from everting during ventricular contraction
-> myocytes are coupled by intercalated discs - electrical + mechanical coupling

• > mechanical (DESMOSOMES like ‘rivets’ holding adjacent cells together)
• > electrical (GAP JUNCTIONS allows easy passage of electrical signals between cells) -> due to this electrical coupling the whole heart behaves like a single cell, i.e. obeys the ‘all or nothing’ law

-> cardiac muscle contractions require CICR