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.