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Unit ii, chapter-2- skeletal system
1. BP101T. Human Anatomy And Physiology-I
(Theory)
Unit-II
2. SKELETAL SYSTEM
Represented By,
Mr. Audumbar Mali.
(Assistant Professor)
Sahyadri College of Pharmacy
Methwade
2. SKELATAL SYSTEM
• Bone tissues makes up about 18% of the total
human body weight.
• The skeletal system supports and protects the
body while giving it shape and form.
• Osteology: It is the branch of science that
deals with the study of the skeletal system,
their structure and functions.
4. FUNCTIONS OF SKELETALSYSTEM
• SUPPORT: Hard framework that supports and anchors the
soft organs of the body.
• PROTECTION: Surrounds organs such as the brain and
spinal cord.
• MOVEMENT: Allows for muscle attachment therefore the
bones are used as levers.
• STORAGE: Minerals and lipids are stored within bone
material.
• BLOOD CELLFORMATION: The bone marrow is
responsible for blood cell production.
5. DIVISIONS OF THE SKELETAL
SYSTEM
• The human skeleton consists of 206 bones.
• Bones of the skeleton are grouped into
two principal divisions:
– Axial skeleton:
• Skull bones, auditory ossicles (ear bones),
hyoid bone, ribs, sternum (breastbone),
and bones of the vertebral column.
– Appendicular skeleton
• Consists of the bones of the upper and lower
limbs (extremities), plus the bones forming
the girdles that connect the limbs to the axial
skeleton.
7. CLASSIFICATION OF BONE BASED
ON SHAPE
• Bones can be classified into five types based on
shape:
• Long
• Short
• Flat
• Irregular
• Sesamoid
8. CLASSIFICATION OF BONE BASED ON
SHAPE
• Long Bones
– Greater length than width and are slightly curved for strength
– Femur, tibia, fibula, humerus, ulna, radius, phalanges
• Short bones
– Cube-shaped and are nearly equal in length and width
– Carpal, tarsal
• Flat bones
– Thin and composed of two nearly parallel plates of compact bone
tissue enclosing a layer of spongy bone tissue
– Cranial, sternum, ribs, scapulae
• Irregular bones
– Complex shapes and cannot be grouped into any of the previous
categories
– Vertebrae, hip bones, some facial bones.
• Sesamoid bones
– Protect tendons from excessive wear and tear
– Patellae, foot, hand
9. THE AXIALSKELETON
The axial skeleton consists of :
1. Skull.
2. Vertebral column (spinal column).
3. Thoracic cage.
4. Sternum.
10. THE AXIALSKELETON
Skull
• The skull is situated on the upper end of vertebral column
and its bony structure is divided into 2 parts.
1. The cranium
2. The face
11. THE AXIALSKELETON
A. Cranium:
• It is formed by flat and irregular bones that provides a bony
protection to the brain.
• 1 Frontal Bone
– It forms the forehead, It forms parts of eye sockets
– The coronal suture joins the frontal and parietal bones.
• 2 Parietal Bones
– It form the sides and roof of the cranial cavity, it articulates
with each other at the sagittal suture.
– It joins the frontal bone with coronal suture and occipital
bone with lambdoidal suture and the temporal bones at
the squamous suture.
• 2 Temporal Bones
– These bones lie one on each side of the head and form
immovable joints with the parietal, occipital, sphenoid and
zygomatic bones.
– The temporal bone articulates with the mendible at the
tempo-mandibular joint.
12. THE AXIALSKELETON
Occipital Bone
– It forms back of head and most of the base of the skull.
– It has immovable joints with the parietal, temporal
and sphenoid bones.
Sphenoid Bone
– It occupies the middle portion of base of skull and it
articulates with the occipital, temporal, parietal and
frontal bones.
Ethmoid Bone
– It occupies the anterior part of base of the skull and
helps to form the orbital cavity, the nasal septum and
the lateral walls of the nasal cavity.
– It is very delight bone containing many air sinuses
that opens into the nasal cavity.
14. THE AXIALSKELETON
B. The Face (Facialbones)
• Nasal Bones
– Form the bridge of the nose
• Maxillae
– Form the upper jawbone
– Form most of the hard palate
• Separates the nasal cavity from the oral cavity
• Zygomatic Bones
– commonly called cheekbones, form the prominences of the cheeks
• Lacrimal Bones
– Form a part of the medial wall of each orbit
• Palatine Bones
– Form the posterior portion of the hard palate
• Inferior Nasal Conchae
– Form a part of the inferior lateral wall of the nasalcavity
15. THE AXIALSKELETON
• Vomer
– Forms the inferior portion of the nasal septum
• Mandible
– Lower jawbone
– The largest, strongest facial bone
– The only movable skull bone
• Nasal Septum
– Divides the interior of the nasal cavity into right and leftsides
– “Broken nose,” in most cases, refers to septal damage rather thanthe
nasal bones themselves
• Orbits
– Eye socket
• Foramina
– Openings for blood vessels , nerves , or ligaments of theskull
18. THE AXIALSKELETON
• The vertebral column:
• Also called the spine, backbone, or spinal column
• Functions to:
– Protect the spinal cord
– Support the head
– Serve as a point of attachment for the ribs, pelvic girdle,
and muscles
• The vertebral column is curved to varying degrees
in different locations
– Curves increase the column strength
– Help maintain balance in the upright position
– Absorb shocks during walking, and help protect the
vertebrae from fracture
20. THE AXIALSKELETON
• The vertebral column:
• Composed of a series of bones called vertebrae
(Adult=26)
– 7 cervical are in the neck region
– 12 thoracic are posterior to the thoracic cavity
– 5 lumbar support the lower back
– 1 sacrum consists of five fused sacral vertebrae
– 1 coccyx consists of four fused coccygeal vertebrae
21. THE AXIALSKELETON
• Intervertebral Discs:
• Found between the bodies of adjacent vertebrae
• Functions to:
– Form strong joints
– Permit various movements of the vertebral column
– Absorb vertical shock
• Vertebrae typically consist of:
– A Body (weight bearing)
– A vertebral arch (surrounds the spinal cord)
– Several processes (points of attachment for muscles)
23. THE AXIALSKELETON
• Thorax: (Thoracic cage)
• Thoracic cage is formed by the:
– Sternum
– Ribs
– Costal cartilages
– Thoracic vertebrae
• Functions to:
– Enclose and protect the organs in the thoracic and
abdominal cavities
– Provide support for the bones of the upper limbs
– Play a role in breathing
24. THE AXIALSKELETON
• Sternum
– “Breastbone” located in the center of the thoracic
wall
– Consists of the manubrium, body, xiphoid process
• Ribs
– Twelve pairs of ribs give structural support to the
sides of the thoracic cavity
• Costal cartilages
– Costal cartilages contribute to the elasticity of the
thoracic cage
27. APPENDICULAR
SKELETON
• The appendicular skeleton consists of :
• 126 bones
• Allows us to move and manipulate objects
• Includes all bones besides axial skeleton
• The limbs
• The supportive girdles
• The Pectoral girdle with the upper limbs and the
Pelvic girdle with the lower limb.
29. APPENDICULAR
SKELETON
Pectoral Girdle
• The human body has two pectoral girdles that
attach the bones of the upper limbs to the axial
skeleton.
• The pectoral girdle consists of :
1. 2 Clavicle ( Collar bone)
2. 2 Scapula (Shoulder blade)
30. PECTORAL
GIRDLE
• Also called the shoulder girdle
• Connects the arms to the body
• Positions the shoulders
• Provides a base for arm
movement
• Consists of
• Two clavicles
• Two scapulae
•Connects with the axial
skeleton only at the manubrium
31. PECTORAL GIRDLE
• The Clavicles
• Also called collarbones
• Long, S-shaped bones
• Originate at the manubrium
(sternal end)
• Articulate with the scapulae
(acromial end)
33. PECTORAL GIRDLE
• The Scapulae
• Also called shoulder blades
• Broad, flat triangles
• Articulate with arm and
collarbone
• Anterior surface: the
subscapular fossa
34. PECTORAL GIRDLE
• The Scapulae
• Structures of the scapula
• Body has three sides:
• superior border
• medial border (vertebral border)
• lateral border (axillary border)
• Body has three corners:
• superior angle
• inferior angle
• lateral angle
35. PECTORAL GIRDLE
• The Scapulae
• The scapular head
• Holds glenoid cavity
• Which articulates with humerus
• To form shoulder joint
• Processes of the glenoid cavity
• Coracoid process:
• anterior, smaller
• Acromion:
• posterior, larger
• articulates with clavicle
• at the acromioclavicular joint
37. THE UPPER LIMB
• The upper limbs consist of the arms, forearms,
wrists, and hands
Note: arm (brachium) = 1 bone,
the humerus
38. THE UPPER LIMB
• The Humerus
• The Shaft
• Deltoid tuberosity:
• a bulge in the shaft
• attaches deltoid muscle
• Radial groove:
• for radial nerve
• posterior to deltoid tuberosity
40. THE UPPER LIMB
• The Forearm (also called the
antebrachium)
• Consists of two long bones
• Ulna (medial)
• Radius (lateral)
41. THE UPPER LIMB
• The Ulna
• The olecranon
• Superior end of ulna
• Point of elbow
• Superior lip of trochlearnotch
• Articulates with trochlea of humerus
• The coronoid process
• Inferior lip of trochlear notch
42. THE UPPER LIMB
• Eight carpal bones
• Four proximal carpal bones
• Four distal carpal bones
• Allow wrist to bend and twist
43. THE UPPER LIMB
• Metacarpal Bones
• The five long bones of the hand
• Numbered I–V from lateral (thumb) to medial
• Articulate with proximal phalanges
• Phalanges of the Hands (14 total finger bones)
• Pollex (thumb)
• Two phalanges (proximal, distal)
• Fingers
• Three phalanges (proximal, middle, distal)
45. THE PELVIC GIRDLE
• Made up of two hip bones (coxal bones)
• Strong to bear body weight, stress of
movement
• Part of the pelvis
• Coxal bones
• Made up of three fused bones
• Ilium (articulates with sacrum)
• Ischium
• Pubis
47. THE PELVIC GIRDLE
• Comparing the Male Pelvis and Female Pelvis
• Female pelvis
• Smoother and lighter
• Less prominent muscle and ligament
attachments
• Pelvis modifications for Childbearing
• enlarged pelvic outlet
• broad pubic angle (>100°)
• less curvature of sacrum and coccyx
• wide, circular pelvic inlet
• broad, low pelvis
• ilia project laterally, not upwards
52. THE LOWER LIMB
• The Patella
• Also called the kneecap
• A sesamoid bone
• Formed within tendon of
quadriceps femoris
• Base attaches quadriceps
femoris
• Apex attaches patellar ligament
53. THE LOWER LIMB
• The Tibia
• Also called the shinbone
• Supports body weight
• Larger than fibula
• Medial to fibula
54. THE LOWER LIMB
• The Fibula
• Attaches muscles of
feet and toes
• Smaller than tibia
• Lateral to tibia
55. THE LOWER LIMB
• TheAnkle
• Also called the tarsus
• Consists of seven tarsal bones
• Bones of the ankle
• Talus:
• carries weight from tibia across trochlea
• Calcaneus (heel bone):
• transfers weight from talus to ground
• attaches calcaneal (Achilles) tendon
• Cuboid:
• articulates with calcaneus
57. THE LOWER LIMB
• Metatarsal Bones of the Foot
• Five long bones of foot
• Numbered I–V, medial to lateral
• Articulate with toes
58. THE LOWER LIMB
• Phalanges of the foot
• Phalanges
• 14 bones of the toes
• Hallux
• Big toe or great toe, two phalanges (distal, proximal)
• Other four toes
• Three phalanges (distal, medial, proximal)
60. ORGANIZATION OF SKELETALMUSCLE
• All activities that involve movement depend on muscles
• 650 muscles in the human body
• Various purposes for muscles for:
• Locomotion
• Upright posture
• Balancing on two legs
• Support of internal organs
• Controlling valves and body openings
• Production of heat
• Movement of materials along internal tubes
• Three types of muscles in the human body
• Skeletal
• Cardiac
• Smooth
61. ORGANIZATION OF SKELETAL MUSCLE
•Skeletal muscles are muscles which
are attached to the skeleton.
•40% of human body mass
•Skeletal muscles are mainly
responsible for locomotion, and
contraction and voluntary relaxation.
62. ORGANIZATION OF SKELETAL
MUSCLE
•Muscle (whole organ)
•Fascicle (portion of muscle)
•Muscle Fiber (single muscle cell)
•Myofibril (muscle cell organelle)
•Sarcomere (portion of myofibril)
•Myofilament (part of sarcomere)
63. STRUCTURE OF SKELETAL
MUSCLE
•Skeletal muscles are composed of clusters of
muscle cells.
• Muscle fibers
• Myofibers
• Myocytes
•A muscle consists of packages of muscle
cells called
fascicles
•A muscle cell is long and spindle shaped
64. STRUCTURE OF SKELETAL
MUSCLE
• Cell structure
• Muscles cells contain many nuclei
• The plasma membrane→ sarcolemma
• The cytoplasm→ sarcoplasm
• Length
• ranges from 0.1cm to more the 30cm in
length
• Diameter
• ranges from 0.001cm to 0.01cm in diameter
• Myofibrils→
• elongated protein molecules
• aligned in parallel arrangements
• extend the full length of the cell.
67. STRUCTURE OF SKELETAL
MUSCLE
The myofibril consists of protein
chains called myofilaments.
• Myofilaments have a
symmetrical, alternating
pattern of thick and thin
elements.
68. STRUCTURE OF SKELETAL
MUSCLE
• Thick myofilament
• consists of a large number of bundled myosin molecules aligned in
overlappingarrays.
• hexameric proteins with two identical heavy chains and two pairs of
different lightchains.
• regulatory light chain (RLC)
• essential light chain (ELC)
69. STRUCTURE OF SKELETAL
MUSCLE
• The thin myofilament (F-actin, filamentous actin)
• made up of two helically intertwined chains of G-actin
(globular actin) units.
• Other proteins that bind to the actin molecules:
• Tropomyosin
• The Troponin complex→ made up of three members
70. PHYSIOLOGY OF MUSCLE
CONTRACTION
• SLIDING FILAMENT MECHANISM :
• The length of skeletal muscle shortens during contraction
because the thick and thin filaments slide over one
another. The process is known as the sliding filament
mechanism.
• The thick filament contains 300 myosin molecules.
• It contain two parts:
1. Myosin tail
2. Myosin heads
• Myosin tail forms the shaft of the thick filament and
heads projects towards the thin filament.
• Thin filament contain actin, troponin and tropomyosin.
71. PHYSIOLOGY OF MUSCLE
CONTRACTION
• Myosin tail forms the shaft of the thick filament
and heads projects towards the thin filament.
• Thin filament contain actin, troponin and
tropomyosin.
• At the onset of contraction, the sarcoplasmic
reticulum release calcium ions into cytosol
• There they bind to troponin and cause troponin-
tropomyosin complexes to move away from
binding site on actin.
• Once the binding sites are free, the repeating
sequence of events of the contraction cycle occurs
that causes the filaments to slide on each other.
72. PHYSIOLOGY OF MUSCLE
CONTRACTION
•The contraction cycle consists of 4 steps
1. ATPhydrolysis.
2. Attachment of myosin to actin to
form cross-bridges.
3. Power stroke.
4. Detachment of myosin from actin.
73. PHYSIOLOGY OFMUSCLE
CONTRACTION
1. ATP hydrolysis :
• The myosin head includes an ATP- binding site
and an ATPase, an enzyme that hydrolyses ATP
into ADP and phosphategroup.
• This hydrolysis gives energy to myosin head.
• ADP and a phosphate group remain attached to
the myosin head.
74. PHYSIOLOGY OF MUSCLE
CONTRACTION
2. Attachment of myosin to
actin to form cross-
bridges:
•The energized myosin head attaches
to the myosin binding site on actin
and releases the previously
hydrolyzed phosphate group.
•When the myosin head attach to
actin during contraction, they are
referred to as cross-bridges.
75. PHYSIOLOGY OF MUSCLE
CONTRACTION
3. Power stroke :
•Once the cross bridges are formed, the
power stroke occurs.
•The cross-bridge rotate towards the
center of the sarcomere and release the
ADPmolecule.
•The cross-bridge generates a force which
slides the thin filament over the thick
filament.
76. PHYSIOLOGY OFMUSCLE
CONTRACTION
4. Detachment of myosin from actin:
•At the end of power stroke, the cross-
bridge remains firmly attached to actin
until it binds another molecule ofATP.
•As ATPbinds to the ATPbinding site on the
myosin head,the myosin head detaches
from actin.
77. NEUROMUSCULAR JUNCTION
• A Neuromuscular Junction is the
synapse or junction of the axon terminal
of a motor neuron with the motor end
plate, responsible for initiation of action
potentials across the muscle's surface,
ultimately causing the muscle to contract.
78. • Morphology:
• The neuromuscular junction is specialized on the
nerve side and on the muscle side to transmit and
receive chemical messages.
• Each motor neuron runs without interruption
from the ventral horn of the spinal cord or
medulla to the neuromuscular junction as a large,
myelinated axon.
• As it approaches the muscle, it branches
repeatedly to contact many muscle cells and
gather them into a functional group known as a
motor unit .
80. • The nerve is separated from the surface of
the muscle by a gap of approximately 20
nm, called the junctional or synaptic cleft.
• The nerve and muscle are held in tight
alignment by protein filaments called basal
lamina that span the cleft between the nerve
and end plate.
• The muscle surface is heavily corrugated,
with deep invaginations of the junctional
cleft—the primary and secondary clefts.
81. The Neuromuscular junction consists of
A)Axon Terminal: contains
around 300,000 vesicles which
contain the neurotransmitter
acetylcholine (Ach).
B) Synaptic Cleft :
20 – 30 nm ( nanometer ) space
between the axon terminal & the
muscle cell membrane. It contains
the enzyme cholinesterase which
can destroy Ach .
C) Synaptic Gutter ( SynapticTrough)
It is the muscle cell membrane
which is in contact with the
nerve terminal . It has many folds
called Subneural Clefts , which
greatly increase the surface area ,
allowing for accomodation of large
numbers of Ach receptors . Ach
receptors are located here .
82. • Formation of Neurotransmitter at
Motor Nerve Endings:-
• The axon of the motor nerve carries electrical signals
from the spinal cord to muscles and has all of the
biochemical apparatus needed to transform the
electrical signal into a chemical one.
• All the ion channels, enzymes, other proteins,
macromolecules, and membrane components
needed by the nerve ending to synthesize, store,
and release acetylcholine and other trophic factors
are made in the cell body and transmitted to the
nerve ending by axonal transport.
83. • Ach formed is stored in
cytoplasm until it is
transported into vesicles for the
release.
85. Ach release
Ca entry into the nerve
Opening of Ca channels
P channels L Channels (slow)
Na influx
Depolarisation
Nerve Action
Potential
86. Ach binds to the post junctionalreceptors
Opening of Na channels
depolarisation
Generation of Action Potential
Transmission of AP along sarcolemma to open Tubular Ca Channels
Muscle Contraction
87. • 1.Upon the arrival of an action potential at the presynaptic
neuron terminal, voltage-dependent calcium channels open
and Ca2+ ions flow from the extracellular fluids into the
presynaptic neuron's cytosol
• 2.This influx of Ca2+ causes neurotransmitter-containing
vesicles to dock and fuse to the presynaptic neuron's cell
membrane. Fusion of the vesicular membrane with the
presynaptic cell membrane results in the emptying of the
vesicle's contents (acetylcholine) into the synaptic cleft, a
process known as exocytosis.
• 3.Acetylcholine diffuses into the synaptic cleft and binds to
the nicotinic acetylcholine receptors bound to the motor
end plate.
• 4.These receptors are ligand-gated ion channels, and when
they bind acetylcholine, they open, allowing sodium ions to
flow in and potassium ions to flow out of the muscle's
cytosol.
88. • 5.Because of the differences in electrochemical gradients across the
plasma membrane, more sodium moves in than potassium out,
producing a local depolarization of the motor end plate known as an
end-plate potential (EPP).
• 6.This depolarization spreads across the surface of the muscle fiber
into transverse tubules, eliciting the release of calcium from the
sarcoplasmic reticulum, thus initiating muscle contraction.
• 7.The action of acetylcholine is terminated when the enzyme
acetylcholinesterase degrades part of the neurotransmitter
(producing choline and an acetate group) and the rest of it diffuses
away.
• 8. The choline produced by the action of acetylcholinesterase is
recycled — it is transported, through reuptake, back into the
presynaptic
terminal, where it is used to synthesize new acetylcholine molecules.
89. Acetylcholine
Ach is synthesized locally in the
cytoplasm of the nerve terminal ,
from active acetate
(acetylcoenzyme A) and choline.
Then it is rapidly absorbed into
the synaptic vesicles and
stored there.
The synaptic vesicles themselves
are made by the Golgi Apparatus
in the nerve soma ( cell-body).
Then they are carried by
Axoplasmic Transport to the
nerve terminal , which contains
around 300,000 vesicles .
Each vesicle is then filled with
around 10,000 Ach molecules.
90. References:
1. Presentation on Introduction To Human Anatomy
& Physiology,
By Mr. Abhay Shripad Joshi.
2. Human Anatomy and Physiology-I,
By Dr. Mahesh Prasad, Dr. Antesh Kumar Jha,
Mr. Ritesh Kumar Srivastav,
Nirali Prakashan, As per PCI Syllabus.
Page No. 2.4 to 2.19.
3. www.google.com.
