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Introduction to Cardiovascular system (CVS)

Consists of :-

1. Heart: serves as a ‘pump’ to impart pressure to blood & to

establish pressure gradient for blood flow .

Heart rate: 72 beats/min (beats 3 billion times in life).

2. Blood vessels: passageways for blood circulation

Length of Blood Vessels: 100,000 KM or 60,000 miles

3. Blood: Transport medium

Volume: 5.5 L

CO : 5L/min, 14000 L/day, 10 million L/yr


Pump The Heart’

Blood Vessels The

circulatory System’

Two closed circuits

1. Systemic circulation

2. Pulmonary circulation

Coronary circulation

(Blood vessels of Heart )

The Heart

• Atrial syncytium

• Ventricular syncytium

• Fibrous insulator

exists between atrium

and ventricle (why?)

• First organ to start functioning in

embryo (3 wks)

Why heart develops and starts

functioning so early ?

1. Circulatory system is transport


2. Very small yolk as food

• Cone shaped, size of closed fist

• Size : 12 cm x 9 cm x 6 cm

(long) (wide) (thick)

• Mass : ♂ 300 gm

♀ 250 gm

• Heart rests on diaphragm

• In midline inside mediastinum (2/3rd

on left side) between vertebral

column & sternum.


The Heart

Heart consists of three layers:

– Endocardium

– Myocardium

– Epicardium

Fibrous skeleton of heart:

– Consists of dense connective tissue

– Four fibrous (C.T) rings, surround valves,

and merge with interventricular septum.


1. Foundation for valve attachment

2. Point of insertion of cardiac muscle

3. Prevents overstretching of valves

4. Serves as electrical insulator

Valves of the heart:

– Formed by dense C.T covered by endothelium

– A.V & SL Valves

– Open and close in response to pressure changes

– Ensure one-way flow of blood

Diseases of valves

Pericardium or Pericardial sac

Normally 5-30 ml clear fluid

Cardiac Muscle

Consist of two kinds of muscle cells

1. Contractile cells: 99%

Atrial & Ventricular Muscles


2. Conducting or Autorhythmic cells:


Impulse generating and conducting

system of heart


• Consists of interlacing bundles of Yshaped

muscle cells, spirally arranged

around the circumference of the heart

• Branching fibers

• Interconnected by intercalated discs

Two types of ‘Membrane Junctions’

– Desmosmes

– Gap Junctions

Has actin and myosin filaments

• Has low resistance intercalated

disks (1/400 the resistance of cell


• Atrial and ventricular “Syncytium”

• No gap junctions between Atrial & Ventricular “Syncytium”

• Abundant mitochondria (Up to 40% of cell volume)

• Heart depends on aerobic energy

• Cardiac muscle has abundant Myoglobin

 To store O2

 To facilitate O2 transport to mitochondria

• No New cardiac muscle is produced after infancy

• The muscle ‘Hypertrophies’ (size of muscle fibers)

• Actin and Myosin filaments in ‘SARCOMERE’

• Sarcotubular system

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One comment

  1. notes are so brief, meant for revision n not first timers

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