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

CVS:

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

system

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.

• CPR

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.

Functions:

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

(Myocardium)

2. Conducting or Autorhythmic cells:

1%

Impulse generating and conducting

system of heart

Myocardium

• 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

membrane)

• 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