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.
- 3. SKELETAL SYSTEM • COMPOSED OF: -Bones -Cartilage -Joints -Ligaments
- 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.
- 6. DIVISIONS OF THE SKELETAL SYSTEM
- 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)
- 32. PECTORAL GIRDLE
- 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
- 36. PECTORAL GIRDLE
- 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
- 39. THE UPPER LIMB
- 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)
- 44. THE UPPER LIMB
- 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
- 49. THE LOWER LIMB •Functions of the lower limbs • Weight bearing • Motion Note: leg = lower leg; thigh = upper leg
- 50. THE LOWER LIMB • Bones of the Lower Limbs • Femur (thigh) • Patella (kneecap) • Tibia and fibula (leg) • Tarsals (ankle) • Metatarsals (foot) • Phalanges (toes)
- 51. THE LOWER LIMB
- 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
- 56. THE LOWER LIMB
- 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)
- 59. THE LOWER LIMB
- 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.
- 84. • How is Ach released…..
- 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.
- 91. THANK YOU