This document summarizes the structure and types of muscle tissue in the human body. It discusses that muscle is composed of actin and myosin filaments that slide to produce movement. There are three main types of muscle: skeletal, cardiac, and smooth muscle. Skeletal muscle is striated and voluntary, attaching to bones via tendons. Cardiac muscle is also striated but involuntary, forming the walls of the heart. Smooth muscle is non-striated and involuntary, found within organs like the digestive tract.

1. Dr. Ayshah Hashimi

2. Introduction
• Muscle is a soft tissue contain protein filament called as Myofilaments of Actin & Myosin that slide over
one another to produce force and motion
• Primarily responsible for maintaining and changing posture, locomotion as well as movement of internal
organs e.g. heart and digestive system
• There are approx. 639 muscles in human body
Properties
• Excitability: ability to respond to stimuli
• Contractability: ability to shorten
• Extensibility: ability to stretch without tearing
• Elasticity: ability to return to its normal shape

3. Structure
• Epimysium is a dense fibrous irregular connective tissue
unsheathing the muscle completely to protect muscles
from friction against other muscles and bones
• Fascicle is bundle of muscle fibers (20-60)
• Perimysium is again a dense fibrous irregular connective
tissue covering a fascicle
• Muscle fibers consists of myofilaments- Actin and Myosin
• Endomysium is areolar tissue that envelopes the plasma
membrane of the muscle fiber called as Sarcolemma
• Epimysium, perimysium and endomysium are all
continuous with each other
• Movement of muscle is from insertion to origin site
• Muscles are rarely directly attached to the bone mostly they are attached vis tendons or aponeurosis

4. Sarcomere is a basic structural and functional unit of muscle. It is a repeating unit between two Z lines
Sarcomere consists of thin filament and thick filament (red colored).
A-Band is a thick band of filament
Between two thick filament is a I-Band
Between two thin filament is H-Zone
M Line
Z Line Z Line
Titins
A-Band
I-Band I-Band
H- Zone

5. Thin filament consists of
• Nebulin (black colored) protein that connects it with Z line
• Actin (blue colored)- present in the form of helix
• Tropomyosin (orange colored) is a protein that binds to the active site of actin molecule during rest
• Troponin (green colored) protein has three binding sites for myosin, tropomyosin and Calcium ion

6. Thick filament consists of
• Myosin protein is a thread like structure arising from thick filament. It consists of tail, neck and two heads
• Within the thick filament is a protein (blue colored) that connects it with the Z-line called as Titin also it
connects protein in the middle of the sarcomere called as M Line (Myomesin, C-protein, Creatine kinase)

7. Types of Muscles
• Skeletal (move bones and other structures)
• Cardiac (forms the wall of the heart)
• Smooth or Visceral (wall of vessels and hollow organs)
• Voluntary muscles (skeletal)
• Involuntary muscles (Cardiac and smooth)
Histological Classification
• Striated muscle (Skeletal and cardiac muscle)
• Non-striated muscle (Smooth muscle)

8. Skeletal Muscle
• Multinucleated, non-branching fibers
• Bounded by endomysium
• Found in many sizes and shape
• Fascicles are arranged into four basic pattern
 Circular
 Fascicles are arranged in concentric rings
 Surround external body openings, which they close by contracting
 Also called as orbicularis or sphincter muscles e.g.
 Convergent
 Has broad origin and converge towards a single tendon of insertion
 Triangular or fan shaped
 e.g. Pectoralis major

9.  Parallel
 Fascicles are arranged along the long axis of the muscle
 3 types- Strap, Fusiform, fan-shaped muscle
 Pennate
 Fascicle are short and run obliquely
 3 forms
 Unipennate
 Bipennate
 Multipennate

10. Cardiac Muscle
• Cells of cardiac muscle has one nucleus
• Broader, shorter and branching fibers (increase surface area for impulse conduction)
• Each chamber of the heart empties by mass contraction, not peristalsis
• Striated but involuntary
• Innervated by autonomic nervous system
• Only myocardium layer of heart has cardiac tissue

11. Smooth Muscle
• Uninucleate
• Narrow, spindle shaped usually lying parallel
• Arranged in longitudinal and circular fashion
• Contractile impulses are transmitted from one cell to another
• Found in the middle layer (Tunica media) of blood vessels and muscular
wall of digestive tract
• Also found in eyeball where it controls lens thickness and pupil size
• Involuntary in nature and innervated by ANS