General Introduction- Muscles

Study of muscles – Myology / Sarcology

Conductivity & contractility are the two main characteristics of muscle.

Voluntary or

skeletal muscles

Involuntary or

smooth musclesCardiac

muscles

Muscles

Voluntary or skeletal muscles

Transverse lines are found at regular interval. Hence these muscles are also called as striped

or striated muscle

Muscle fibre is covered by a layer of connective tissue which is called Endomysium, Many

muscle fibers are combined to form fasciculi, covered by Perimysium

Many fasciculi combined to form a muscle, is also covered by a layer of connective tissue

which is called as Epimysium

Muscle fibres attached to a tough cord of connective tissue called Tendon & Tendon is

further attached with a bone.

LOCOMOTION AND MOVEMENT:

Structure of muscle fibre

Fine structure of muscle fibre:

Outer membrane of muscle fibre is sarcolemma enclosed a

multinucleated sarcoplasm

Myofibril are arranged in parallel row & form the dark & light

line made up of actin & myosin protein.

Actin filaments are thin while myosin filaments are thick

Light band made up of only actin filament, these band are

monorefractive in polarised light so it is called Isotropic

band (I band).

Actin filaments are connected with Z–line protein (Actinin)

which is called as Z line (Zweichenschiebe) or (Double's

membrane) or (Krause's membrane).

Dark line is made up of actin & myosin, is double monorefractive in polarised light

due to overlapping so it is called Anisotropic band.

Terminal end of actin filament are embedded among the myosin filament so peripheral part of a

band is darker as compared to the middle part of A band called as H-Zone or Hensen zone

Diagrammatic representation of

(a) anatomy of a muscle fibre

showing a sarcomere

(b) a sarcomere

Chemical Composition of Skeletal Muscles

A dark line is also found in the central part of H-zone which is called as M line.

The distance between two Z–lines is Sarcomere.

Sarcomere = 1A band + two half I band.

1 Myosin filament is surrounded by 6 Actin filaments & 1 Actin filament is surrounded by 3

Myosin filaments.

Chemical Composition of Skeletal Muscles

75% water 25% solid

20% Muscle proteins 5% other substance

Sarcoplasmic protein, Globin, Globulin,

Myoglobinate

Contractile

proteinNitrogenous

extractive

Creatine & creatine

phosphate

Nonnitrogenous

extractive

Glycogen

Inorganic ion

Eg. K+, Na+, HCO3Force generating Regulating Structure

Proteins

Actin

Myosin

G-Actin

F-Actin

Z line Proteins

(Actinin)

Proteins

Tropomyosin

Troponin (TP)HMM

LMM

Various Types of Protein

Force Generating Protein

Actin is a double helix made up of protein molecule

called as G–Actin. (Globular actin)

G-actin contain a active site for attachment of myosin

head.

Myosin (Thick) Filament is also a polymerized

protein, made up of meromyosin monomer.

Meromyosin has two important parts, a globular head with a short arm HMM (Heavy

meromyosin) and a tail LMM (Large meromyosin)

Regulating protein

Tropomyosin is one type of contractile protein. In the relaxed state of the muscle situated

in such a way, that the active sites remain covered by the tropomyosin & attached at the

terminal end of actin.

Troponin is one type of protein which attached with one of ends of the tropomyosin

molecules.

Troponin is made up of three subunit • Troponin I (Inhibitory site)

• Troponin T (Tropomyosin site)

• Troponin C (Ca+2 binding site) Structural protein

Actinin is one type of protein which found in Z–line.

Sliding filament theory -

Sliding filament theory

At motor end plate large number of vesicles & mitochondria are present. Each vesicle

contains Ach in high concentration. In post junctional membrane, Ach receptor are

present on post junctional membrane.

Given by A.F. Huxley, H.E. Huxley & J. Hansen

At neuromuscular junction

terminal branches of Axon form

a bulb like structure is called as

motor end plate.

Sarcolemma invaginate inside

& form a fimbriated structure

which is called synaptic gutter

or subneural cleft.

The cell membrane of the bulbous

terminal pre junctional

membrane cell membrane of

muscle fibre called post junctional

membrane.

Motor nerve fiber stimulated develops an Action potential.

AP reaches in the neuromuscular junction & goes to bulbous expansion of the nerve

terminal than it increases permeability of Ca++ in the pre junctional membrane

Ca++ ions causes bursting of the vesicles & releases the Ach

Ach now cross the prejunctional membrane. via subneural cleft reach the post

junctional membrane & attach the Ach receptor

Stimulate & develop end plate potential by opening of Na+ Voltagegates channels,

and when it is higher than A.P., this AP initiate the muscle contraction.

Sarcolemma invaginate inside & form transverse & longitudinal tubules which are

also called as T-tubule and L-tubule

T-tubules are parallel to Z-line whereas L-tubule is perpendicular to the Z-line.

L–tubules dilated on both side of T–tubules this dilated part called terminal cisterns.

A.P. proceeds along the sarcolemma & A.P. contact with T–tubules & further proceeds

via T–tubules & enter with in muscle fibre & now this AP called as T–tubule potential.

T–tubule potential come in close contact of L–tubules at region of the Triads (T+ L–

tubules).

L–tubules has a rich source of Ca++ ion, releases Ca++ ion combine with troponin C

Tropomyosin move away of active site of actin and form Actomyosin complex.

Myosin head twists in the groove of the active site of actin–F. This causes

movement of actin towards H zone.

Contraction is caused by overlapping of actin filament over myosin filament –

sliding filament hypothesis

After muscle contraction H–zone disappears & length of sarcomere & I-band decreases

by 20%. Length of A band remains unchanged.

Physiology of Muscle Contraction

Role of ATP

The Rotational movement of myosin head with in

the groove.

Detachment of myosin head from the actin.

Motor nerve fiber

Opening of voltage gated calcium channels

Action potential

Entry of calcium ions from ECF

Opening of vesicles and release of AchAxo

n t

erm

inal

Synaptic cleft Passage of Ach

Binding of Ach with receptor and

formation of Ach-Receptor complex

Opening of ligand gates sodium channels

Po

sts

yn

ap

tic m

em

bra

ne

Development of end plate potential

Generation of action potential

Muscular contractionMu

scle

fib

er

Chemical Reaction in Muscles

ATP + H2OCreatine kinase

ADP + Pi + Energy(For contractile muscle)

Creatine phosphate + ADP → Creatine + ATP(Muscle contraction)

GlycogenGlycolysis

Lactic acid + Energy

80% Lactic acid +WaterATP

Glycogen (Liver Cell)

20% Lactic acid + Oxygen → CO2 + H2O + ATP (Liver Cell)

Creatine + ATP → Creatine phosphate + ADP(Resting Muscle)

Involuntary Muscle

Found in the visceral organ so are called as visceral muscles or smooth muscles.

Transverse lines are absent,

Unstriated muscle.

Fibres are spindle shaped, cells are

connected through gap junction.

Contractile fibrils or myfibers are

found in the cytoplasm called

sarcoplasm.

Myofibril are made up of actin & myosin

Sarcoplasmic reticulum or L tubular system is not well developed. This makes the

contraction of smooth muscles strongly dependent on the ECF Ca++ ions.

It remain in contracted stage for longer hence called No fatigue muscle.

Smooth and Cardiac Muscles

Involuntary Muscle

Single Unit

Multi Unit

Compact muscles where the individual cells joined together by gap junctions.

Muscular activity is initiated due to hormonal action, stretching and other

stimulations.

Occur in the wall of gastrointestinal tract, fallopian tube, uterus, ureter, urinary

bladder.

When completely denervated these smooth muscle continue contracted rhythmically.

Muscle fibres occur in small groups, inervated separately and contract

independently.

Found in

• Nictitating membrane (iris)

• Pilomotor muscle in the hair follicle. (Skin)

Arteriolar Smooth Muscle – Both type of properties found

Smooth and Cardiac Muscles

Cardiac Muscle

Striated type of muscle, it is also cylindrical fibre. Fibre are branched.

Transverse septa are found in the muscle fibre which are called as intercalated disc.

Septa fibres are divides fibre into many segments each segment is Uninucleated.

Involuntary muscles & control by pacemaker (SA, AV & Purkinje fibres).

Difference between Striated, Non striated and Cardiac

Striated Non striated Cardiac

They are present in upper

limb & lower limb etc.

Iris of eye (Ciliary muscle of

eye)

Urinary bladder, Urinogenital

tract, Dermis of skin

They are present in walls of

Heart

Cylindrical Erector pill muscle of dermis Cylindrical

Fibres Unbranched Spindle in shaped Fibres are branched

Multi Nucleated fibres Unbranched Uninucleated

Light and Dark band present Uninucleated Present

Oblique bridges and

Intercalated disc absent

Absent

AbsentPresent

Controlled by CNS ANS Both CNS + ANS

Blood supply abundant Less Richly blood supply

Soon fatigue Do not get fatigue Never fatigued

Properties of muscles -

Origin - fixed end of muscle (Proximal end),

Insertion - Distal end of muscle which is attach to

bone (Movable end).

Excitability responds to stimuli

Conductivity stimulus acting in one region of

muscle fibres propagated to all parts.

Contractility fibres contract & shorten followed by

relaxation.

Threshold Stimulus intensity of stimulus below the threshold value which does not produces

contraction in muscle fibres is called subthreshold stimulus, stimulus stronger than threshold

one is called suprathreshold stimulus.

All or none law is followed by muscles

Muscle twitch

Latent period is the interval between the application of appropriate stimulus & initiation of

contraction, 0.01 sec. in skeletal muscle 3 sec. in smooth muscle.

Contraction phase - When muscle remain in contracted state, 0.04 sec. in skeletal muscle. 20 sec. in smooth muscle

Relaxation phase - Interval for contracted muscle to regain its original/relaxed state 0.05 sec. in skeletal muscle. 23 sec. in smooth muscle.

Muscle curve

Refractory period is period between two twitches when muscle does not

respond to second stimulus, 0.002 - 0.005 second in skeletal muscles and 0.1 -0.2 second in visceral muscles

Summation of stimuli - two subliminal stimuli Applied simultaneously get added up &

Evoke the response,

Muscle response = (1st stimulus subliminal + 2nd stimulus subliminal > threshold value)

Few fibres always undergoing

contraction alternately so

maintain the health of

muscles, known as Muscle tone.

Tetanic condition - It is sustained muscles contraction

due to hypocalcaemia and

hormonal deficiency disease

It is bacterial disease

(Clostridium tetani) lock jaw disease

Paralysis motor nerve impulse completely cut off.

Shivering - Involuntary contraction of muscles.

Tetany Tetanus

Muscle tension force produced during contraction.

Muscle tension

Isomeric contraction Isotonic contraction

Length same but tone changed

(Work done is zero)

E.g.. Pushing against an immovable object.

Length changed but tone same

E.g.. Walking, Load is lifted.

Antagonistic muscles causes opposite movement at the same site when one muscle is

contracting, the other is relaxes & vice versa. e.g. - Biceps (flexor) & Triceps of arms (extensor)

Cori cycles – lactic acid transported in blood as blood lactate to

liver where it changes into liver glycogenPyruvic acid

Lactic acid

Muscle

glycogen

Liver

glycogen

Blood glucose

Cori cycle

Fatigue – Due to sustained contraction ATP is exhausted & muscle

is a state of permanent contraction & no relaxation because

1. Accumulation of lactic acids

2. Consumption of stored glycogen, ATP, CTP

Rigor Mortis – After death due to non availability of ATP/C.P.

detachment of myosin from actin cannot take place result in

permanent state of contraction of muscle.

General Introduction - SKELETAL SYSTEM

SKELETAL SYSTEM

Exoskeleton

This is developed from epidermis.

Example Hair, Nails, Claws, Hoof &

Horns feathers, etc. Exoskeleton is

ectodermal in origin & nonliving.

Endoskeleton

It is present inside the body &

mesodermal in origin, in vertebrate

endoskeleton is formed of bone and

cartilage.

Human Skeleton

Endo skeleton

Axial skeleton

Skull

Vertebral column

Ribs

Sternum

Appendicular Skeleton

Limbs

Girdles

Humerus – 1 + Radius and Ulna – 2 + Carpals – 8 +

Metacarpals – 5 + Phalanges – 14

THE HUMERUS

Head It articulates with the glenoid cavity

form shoulder joint.

Deltoid ridge (V-shaped), elevated

rough part on the shaft where deltoid

muscle is attached

Lower end, Articulates laterally with

radius & medially with ulna.

Coronoid fossa accommodates the Coronoid process of ulna when elbow

Olecranon fossa accommodates the olecranon process when Elbow is extended

The Radius And Ulna

Radius

Head, covered with hyaline cartilage, superior

concave surface articulates with the capitulum

Circumference of head is also articulated it fits into socket

formed by the radial notch of the ulna to form radioulnar joint.

Inferior surface - Bears a area for the scaphoid bone & lunate

bone.

Ulna Bone

Trochlear notch - Trochlea of humerus fits in this notch

Coronoid process forms base of trochlear notch.

Lower end articulator with carpals

Olecranon process - Projects upwards from shaft of ulna. It is responsible for making elbow joint.

Carpal Bones

Proximal row (From lateral to medial) – Scaphoid, lunate, triquetrum, pisiform

(sesamoid bone)

Distal Row : Trapezium, trapezoid, capitate, Hamate

Metacarpal bones : 5 Bones

Phalanges are 14, 3 for

each finger and 2 for the

thumb.

Bones Of Hind Limb

FEMUR

Femur – 1 + Patella – 1 + Tibia and tibula – 2 + Tarsals – 7 + Melatarsals – 5 + Phalanges – 14

Articulates with acetabulum to form

the hip joint.

Lower end has two large condyles, one medial & one lateral

Patella bone located in the patellar

groove of femur bone upon knee

joint.

Head

TIBIA

Upper end has two large

condyles which articulates

with femur bone

FIBULA

Upper end articulates with the lateral condyle of tibia, it does not participate in the formation

of knee joint.

It lower end fused with tibia and form inferior tibiofibular joint (immovable joint)

Tarsals

Proximal row: Talus above, Navicular in between and Calcaneum below.

Talus is second largest tarsal bone

Calcaneum: Largest tarsal bone. Communicate body weight towards posterior during

standing condition.

Distal row: Four tarsal bones lying side by side (three cuneiforms and one cuboid)

Meta tarsuls

Made of 5 meta tarsal bones

Phalanges

14 Phalanges, 2 for great toe & 3 each

for other four toes.

PECTORAL GIRDLE

Pectoral girdle: Each pectoral girdle consists of two bones i.e. Scapula + Clavicle

Scapula has 3 process which provide attachment to muscles

• Spinous process

• Acromion process

• Coracoid process

It also has a glenoid cavity to

accommodate head of Humerus

Medial End: Articulates with the clavicular

notch of manubrium

Lateral End: Bears a facet which

articulates with acromion process of

scapula

Pelvic girdle (Hip bone)

Also called as innominate or coxal bone, made by fusion of three bones; Superiorly –

Ilium, Anteroinferiorly – Pubis. Postero inferiorly – ischium.

At the point of fusion of above bones is a cavity called acetabulum to which thigh bone

articulate.

Two halves of the pelvis girdle meet ventrally to form the pubic symphysis containing

fibrous cartilage.

Sternum

Sternum divided into Manubrium, body and xiphoid process.

Manubriums lateral border joints with first rib pair.

In its clavicular notch, clavicle bone articulates.

Body (Middle part) forms joint with lower part of 2nd C.C. & 3rd to 6th C.C. & upper

half of 7th CC

Lower part Xiphoid process, Smallest part, lower half of 7th C.C. articulates.

THE RIBS

12 pairs of ribs connected dorsally to the

vertebral column and ventrally to sternum.

Rib has two articular surfaces hence called

as bicephalic.

First 7 ribs are True Ribs, Vertebrosternal ribs

Remaining 5 are False Ribs, 8th, 9th & 10th

ribs are Joined to the next higher cartilage,

called Vertebrochondral ribs, 11th & 12th ribs

are free & are called floating ribs (Vertebral

ribs).

Costal cartilages are unossified anterior parts

of ribs are made of hyaline cartilage

C.C. of first seven ribs are directly attached

to sternum. 8th, 9th & 10th C.C. articulate

with one another. The cartilage of 11th & 12th ribs are small.

THE VERTEBRAL COLUMN

Made of 33 vertebrae or 26 bones

Formula = C7T12L5S 5 C(4), ∴ 24

movable or true vertebrae and (5) +

(4) = 9 fused or false vertebrae

(immovable) Sacrum & coccyx.

Vertebral column has 4 curvatures

which are known as cervical,

thoracic, lumber and pelvic

curvature.

Cervical vertebrae

All cervical vertebrae have Foramina transversal is which aligned to form vertebrarterial

canal through which artery passes.

Spinous process of cervical vertebrae is bified (Except C7)

The number of cervical vertebrae are seven

Atlas (𝐂𝟏)

Centrum and Pre and postzygapophysis

processes are absent

The foramen divided into two parts by a

ligament. In upper part, spinal cord is

present. In lower part, Odontoid fossa is

present in which odontoid process of axis

is fitted to make medial Atlanta-axial joint

(Pivot Joint).

Articular facets are present. In upper pair

of articular facets condyles of skull are

fitted to make Atlanto-occipital joint, in

lower pair of articular faceles condyles of

axis are fitted to make lateral Atlanto-

axial joint.

Atlas and Axis

Atlas (𝑪𝟐)

Centrum present, Neural spine well

developed and bifid. Prezygapophysis

processes are absent but post

zygapophysis processes are present.

Other Vertebrae

Thoracic Vertebrae

They are identifying by the presence of costal demifacetes.

On their transvers processes articulates ribs

Lumbar vertebrae are the largest sized

vertebrae because they have to support the

weight of upper body

SACRUM formed by fusion of five sacral

vertebrae, it is large Hat and triangular bone

Coccyx formed by fusion of 4 coccygeal

vertebrae.

SKULL

Skull consist of 29 bones

Cranium – 8

Face – 14

Ear Ossicles – 3 + 3 = 6

Hyoid – 1

All skull bones (except mandible & ear ossicles) are immovable

Cranium (Brain box) encloses the brain, has large opening called foramen magnum

Cranium:

Cranium Bones – [8]

All these bones of skull are joined together by suture,

E.g. (1) Coronal suture: Between the frontal and parietal bone

(2) Lambdoid suture: Between parietal and - occipital

Frontal bone [1] forms the forehead and

roofs of eye sockets

Parietals bones [2] form the roof of

cranium and maximum part of side of

cranium.

Occipital bone [1] has magnum is present,

on each side of this foramen one condyle is

present called as occipital condyle which fit

in particular faceted of atlas vertebrae. So

the human skull is dicondylic.

Temporal bones [2] form the lower parts of each sides of cranium.

In the house of this bone internal and middle ear are present - Malleus, incus,

stapes.

Sphenoid bone [1] forms middle and anterior part of base of cranium.

It articulates with frontal bone occipital bone and temporal.

In this bone Sella turcica is present in which pituitary gland is situated.

Ethmoid bone [1] in front of sphenoid and behind nasal bones.

Sensory capsule

1. Malleus (Modification of articular bone)

2. Incus (Modification of Quadrate bone)

3. Stapes modification of Hyomandibular bone

Facial - Bones

Nasal bones [2] forms dorsal surface of nasal chambers.

Inferior turbinal’s [2] situated on lateral surface of more. There projections are called

turbinels which projected into nasal cavity

Vomer [1] present is posterior part of nasal chambers.

Lachrymal [2] located in the lateral sides of nasal bones, also form a part of the wall

of eye sockets.

Zygomaticus or malar bones also called as cheek bones. Forms the prominences of

our cheeks.

Palatines [2]: 'L' shaped bones that form the (posterior) part of our hard palate

Maxillary [2]: Large, upper jaw bones that form the major part of our face and upper

jaw comprise anterior part of our hard palate.

Mandible [1] is only movable bone of skull. In the posterior part of this bone condyle is

present which fit in the cavity of temporal bone

Lower jaw is attached with cranium this suspension is called craniostylic.

Hyoid bone [1] (Tongue bone) between lower jaw and larynx, it is not articulated to any bone of axial skeleton.

JOINTS - 1

Fibrous joints (Immovable) or Synarthrosis

Synovial joints or Diarthrosis

Cartilaginous joints (Slightly movable) or Amphiarthrosis

Sutures - Immovable: e.g. Skull

Syndesmosis: Bones are connected by interosseous ligament e.g. inferior tibio fibular joints

Gomphosis – e.g. tooth in its socket

Primary or synchondrosis, after certain age the cartilage is replaced by bone. e.g. joint between Epiphysis & Shaft

Secondary or Symphysis fibro cartilage or hyaline cartilage is present between two bones at joint. e.g. Symphysis pubis, intervertebral disc, between rib and sternum.

Plain synovial or gliding joint: Permit slight gliding movement e.g., joint between zygapophysis, between carpals, between tarsals processes of vertebrae

Hinge Joint: Movements are permitted in one plane around transverse axis e.g. elbow joint, ankle joint, interphalangeal joint, knee joint

Pivot Joint: movement are permitted in one plane around vertical axis. e.g. radioulnar joint, median Atlanta axial joint.

JOINTS - 2

Condylar joint: Movement are permitted in both transverse & vertical axes. E.g. Jaw joint,

Knee joint, Atlanto-Occipital joint.

Ellipsoid joint: Movement are permitted in both axis. e.g. Wrist joint,

Metacarpophalangeal joint.

Saddle Joint are improperly developed ball & socket joints e.g. first carpometacarpal joint.

Ball & socket joint: Movements are around infinite axis. e.g. Shoulder & Hip joint.

Disorders of Bones:

Arthritis

Caused by the inflammation of the joints.

The rheumatoid arthritis: It is diagnosed by the presence of rheumatoid factor (a type of immunoglobulin IgM).

Primary symptom inflammation of synovial membrane

If it is left untreated, membrane then starts secreting abnormal granules, called pannus,

which after accumulating on the surface of the cartilage, cause its erosion. As a result, the

fibrous tissues are attached with the bones and become ossified, making the joints immovable.

Osteoarthritis characterized by the degeneration of the articular cartilage, afflicted joints are of spine, knees and hands.

Gouty arthritis or gout caused either due to excessive formation of uric acid, gets deposited in joints as monosodium salt.

Osteoporosis characterized by decreased bone mass increased changes of tractures. Decreased level of estrogen is a common cause.