histology cardiac muscle

Cardiac muscle

It is striated involuntary, it contracts spontaneously

Site

Wall of the heart and origin of big vessels

LM cardiac muscle

It has smaller diameter

The cardiac muscle fiber is branching and anatomizing

Each fibers is former of many cells

Each cell is branching and anatomizing with each other

Adjacent cells are connected tgt by intercalated discs

Each cell has one,large oval central nucleus.

Cytoplasm acidophilic and has glycogen and lipid granules

No satellite cells so cardiac muscle fibers can’t regenerate

WITH E.M

Myofibrils and myofilaments

Sarcoplasmic reticulum and T-tubules

Intercalated discs

Numerous mitochondria

Atrial granules

Golgi apparutus small

Inclusion glycogen lipid and lipofuscin on either sides of the nucleus

Myoglobin for oxygen supply

Myofibrils and myofilaments

-cardiac myofibrils are branching and anastomosing. Cross striation are not regular.

Myofilaments the same as skeletal Muscle

Sarcomere as skeletal muscle

Sarcoplasmic reticulum and T tubules

• T- tubules are wide and are present at Z line

• Sarcoplasmic reticulum is poorly developed

• Terminal cisternae is a single beside each T-tubule DIAD at the Z line

• Function same as skeletal muscles

Intercalated disk

It is special type of junction between cardiac muscle cells

It is step like

It is formed of two parts transverse portion and lateral portion

Transverse part

It is present at right angle to muscle fiber

It has 3 components

-fascia adherens and macula adherens prevent detachment of muscle fiber during contraction mechanical coupling

Few gap junctions

Lateral L.S part

Parallel to muscle fiber

It has numerous gap junctions for ionic coupling coordinated muscle contraction as one functional unit

Atrial granules

They are present in atrial muscle fibers

Present on either sides of the nucleus

They contain a precursor of a hormone atrial natiuretic factor ANF

Atrial granules function

Decrease blood pressure

Growth of cardiac muscles

Hypertrophy

Regeneration cardiac muscles

No stallite cells, so cardiac muscles can’t regenerate and healing occurs by fibrous tissue myocardial infraction

Impulse conducting system of the heart

It consists of SA node, AV node, A-V bundle and their branches.

Moderator band

It is the right branch of A-V bundle

It has special type of cardiac muscle fibers purkinji fibers which have

Few myofibrils

No diad system

Few intercalated disc

Larger in diameter

Pale and vacuolated rich in glycogen

Rich nerve supply

Quick impulse conduction