1. Explain the structure of bone with diagram.
Answer: Bone is a specialized, hard connective tissue that forms the skeleton. It provides support, protection, movement, mineral storage, and blood cell production.
Macroscopic Structure:
Diaphysis: The long shaft of the bone. It is composed of compact bone and contains the medullary cavity (marrow cavity). Epiphyses: The expanded ends of the bone. They are composed of spongy bone covered by articular cartilage. Periosteum: A tough, fibrous membrane covering the outer surface of the bone (except at joints). It contains osteoblasts and osteoclasts. Endosteum: A thin membrane lining the medullary cavity. Medullary Cavity: Contains yellow marrow (fat) in adults and red marrow (blood cell production) in children.
Microscopic Structure (Compact Bone):
Osteon (Haversian System): The functional unit of compact bone. Haversian Canal: Central canal containing blood vessels and nerves. Lamellae: Concentric rings of bone matrix around the Haversian canal. Lacunae: Small cavities between lamellae containing osteocytes. Canaliculi: Tiny canals connecting lacunae, allowing communication between osteocytes. Volkmann's Canals: Canals that run perpendicular to Haversian canals, connecting them.
Microscopic Structure (Spongy Bone):
Trabeculae: A network of thin, branching plates of bone. Spaces: Filled with red bone marrow.
Diagram Description: (A diagram would show a long bone with diaphysis, epiphysis, periosteum, medullary cavity, and a magnified view of an osteon with Haversian canal, lamellae, lacunae, and canaliculi.)
In summary, bone has a complex structure adapted for its many functions, from macroscopic features to microscopic organization.
2. Explain the structure of cartilage with diagram.
Answer:
Cartilage is a flexible, semi-rigid connective tissue that provides support, reduces friction at joints, and serves as a precursor for bone in developing embryos.
Structure:
Chondrocytes: Mature cartilage cells. They are found in small cavities called lacunae. Extracellular Matrix: The matrix is produced by chondrocytes. It consists of:
Collagen fibers: Provide tensile strength. Elastic fibers: Provide flexibility. Proteoglycans: Provide resilience and hydration.
Perichondrium: A layer of dense irregular connective tissue surrounding cartilage (except at joints). It contains chondroblasts (cartilage-forming cells).
Types of Cartilage:
1. Hyaline Cartilage:
Most common type. Matrix: Collagen fibers (invisible). Locations: Articular surfaces of bones, ribs, nose, trachea, larynx. Function: Smooth surface for joints, flexibility, support.
2. Elastic Cartilage:
Matrix: Elastic fibers (visible). Locations: External ear, epiglottis. Function: Maintains shape, provides flexibility.
3. Fibrocartilage:
Matrix: Thick collagen fibers (visible). Locations: Intervertebral discs, pubic symphysis, menisci of knee. Function: Shock absorption, tensile strength.
Diagram Description: (A diagram would show chondrocytes in lacunae surrounded by the extracellular matrix.)
Growth:
Appositional: New cartilage added on the surface. Interstitial: Chondrocytes divide within lacunae.
In summary, cartilage is a specialized connective tissue with diverse types and functions. Its structure is adapted for flexibility, support, and shock absorption.
3. Describe the bones of appendicular and axial skeleton of man.
Answer: The human skeleton is divided into the axial and appendicular skeletons.
Axial Skeleton (80 bones):
Skull (22 bones):
Cranium (8): Frontal, parietal (2), temporal (2), occipital, sphenoid, ethmoid. Protects the brain. Facial bones (14): Maxilla (2), mandible, zygomatic (2), nasal (2), lacrimal (2), palatine (2), inferior nasal conchae (2), vomer.
Hyoid Bone (1): U-shaped bone in the neck, supports the tongue.
Vertebral Column (26 bones): Cervical (7), Thoracic (12), Lumbar (5), Sacrum (1 fused), Coccyx (1 fused). Thoracic Cage (25 bones): Ribs (24, in 12 pairs) and Sternum (1).
Appendicular Skeleton (126 bones):
Pectoral Girdles (4 bones): Clavicle (2) and Scapula (2). Upper Limbs (60 bones): Humerus (2), Radius (2), Ulna (2), Carpals (16), Metacarpals (10), Phalanges (28). Pelvic Girdle (2 bones): Hip bones (ilium, ischium, pubis fused). Lower Limbs (60 bones): Femur (2), Patella (2), Tibia (2), Fibula (2), Tarsals (14), Metatarsals (10), Phalanges (28).
In summary, the axial skeleton forms the central axis and protects vital organs, while the appendicular skeleton allows for movement and manipulation of the environment.
4. Describe the bones of cranium.
Answer: The cranium (skull) is composed of eight bones that enclose and protect the brain.
1. Frontal Bone (1):
Forms the forehead, roof of the orbits, and anterior part of the cranial floor. Contains the frontal sinuses.
2. Parietal Bones (2):
Form the sides and roof of the cranium.
3. Temporal Bones (2):
Form the sides and base of the cranium.
Contain the external auditory meatus (ear canal), mastoid process, styloid process, and zygomatic process. House the middle and inner ear structures.
4. Occipital Bone (1):
Forms the back and base of the cranium. Contains the foramen magnum (opening for the spinal cord) and occipital condyles (articulate with atlas).
5. Sphenoid Bone (1):
Butterfly-shaped bone in the middle of the skull base. Articulates with all other cranial bones. Contains the sella turcica (hypophyseal fossa) which holds the pituitary gland.
6. Ethmoid Bone (1):
Located between the eyes. Forms part of the nasal septum, orbital walls, and cranial floor. Contains the cribriform plate (olfactory foramina).
Sutures:
Coronal, sagittal, squamous, lambdoid.
In summary, the cranium is a complex structure of eight bones that protect the brain and support the face.
5. What are the following common types of disorders of human skeleton: a. Slipped disc, b. Spondylosis, c. Sciatica, d. Arthritis
Answer:
a. Slipped Disc (Herniated Disc):
Cause: The soft inner material of an intervertebral disc protrudes through a tear in the outer ring. Symptoms: Back pain, numbness, tingling, weakness in limbs. Treatment: Rest, pain relievers, physical therapy, surgery.
b. Spondylosis:
Cause: Degenerative changes in the spine (osteoarthritis of the spine). Symptoms: Stiffness, pain, reduced mobility. Treatment: Exercise, pain relievers, physical therapy.
c. Sciatica:
Cause: Compression or irritation of the sciatic nerve, often due to a herniated disc. Symptoms: Sharp, shooting pain from the lower back down the leg. Treatment: Rest, pain relievers, physical therapy, surgery.
d. Arthritis:
Cause: Inflammation of one or more joints. Types: osteoarthritis (wear and tear), rheumatoid arthritis (autoimmune), gouty arthritis (uric acid crystals). Symptoms: Joint pain, stiffness, swelling, reduced range of motion. Treatment: Medications, physical therapy, surgery, lifestyle changes.
6. Give a detail account of bone repair.
Answer: Bone repair is the process by which a fractured bone heals. It occurs in four main stages.
1. Hematoma Formation:
Immediately after a fracture, blood vessels in the periosteum and bone are torn, causing bleeding. A blood clot (hematoma) forms at the fracture site. Inflammatory cells (macrophages) remove dead tissue.
2. Fibrocartilaginous Callus Formation:
Fibroblasts and chondroblasts from the periosteum and endosteum migrate to the fracture site. They produce collagen fibers and cartilage, forming a soft callus (fibrocartilaginous callus). This callus bridges the gap between the broken bone ends.
3. Bony Callus Formation:
Osteoblasts migrate to the callus and begin to produce spongy bone. The soft callus is gradually replaced by a hard bony callus. This stage takes several weeks.
4. Bone Remodeling:
Osteoclasts and osteoblasts work to reshape the bone. Excess bone is removed, and the bone is restored to its original shape and strength. This stage can take months to years.
Factors Affecting Bone Repair:
Age, nutrition, blood supply, and the type of fracture.
In summary, bone repair is a complex, multi-stage process that restores the integrity of the bone.
7. Give an account of the following related to injuries to bones: a. Dislocation of joints, b. Sprain, c. First aid treatment for disorders of skeleton
Answer:
a. Dislocation of Joints:
Definition: Displacement of a bone from its normal position in a joint. Cause: Trauma, fall, or sudden movement. Symptoms: Severe pain, swelling, deformity, inability to move the joint. Treatment: Immobilization, reduction (realignment) by a doctor, rest, rehabilitation.
b. Sprain:
Definition: Overstretching or tearing of ligaments. Cause: Twisting or wrenching movement. Symptoms: Pain, swelling, bruising, limited movement. Treatment: RICE (Rest, Ice, Compression, Elevation), pain relievers, physical therapy.
c. First Aid Treatment for Skeletal Disorders:
Fractures: Immobilize the area with a splint. Do not move the person if a spinal injury is suspected. Apply ice to reduce swelling. Seek medical help. Dislocations: Immobilize the joint. Do not attempt to realign it. Apply ice. Seek medical help. Sprains: RICE. Avoid using the injured area.
In summary, prompt and proper first aid is crucial for minimizing damage and promoting recovery from skeletal injuries.
8. Describe three types of muscle tissues in man.
Answer: There are three types of muscle tissue in the human body: skeletal, smooth, and cardiac.
1. Skeletal Muscle:
Structure: Striated (alternating light and dark bands), multinucleated, cylindrical fibers. Control: Voluntary (under conscious control). Location: Attached to bones. Function: Movement, posture, heat production.
2. Smooth Muscle:
Structure: Non-striated (no bands), spindle-shaped cells, single nucleus. Control: Involuntary. Location: Walls of internal organs (stomach, intestines, blood vessels, bladder). Function: Movement of substances (peristalsis), regulation of blood flow.
3. Cardiac Muscle:
Structure: Striated, branched fibers, single nucleus, intercalated discs. Control: Involuntary. Location: Heart. Function: Pumping blood.
In summary, each muscle type has a unique structure and function suited to its role in the body.
9. Explain the ultra structure of skeletal muscle.
Answer: Skeletal muscle is composed of highly organized structures that enable contraction.
Hierarchical Organization:
Muscle: Made of bundles of fascicles. Fascicle: Made of bundles of muscle fibers. Muscle Fiber (Cell): A single, multinucleated cell. Myofibril: Cylindrical structures within the muscle fiber. Sarcomere: The functional unit of contraction, repeating along the myofibril.
Ultrastructure of a Sarcomere:
Z lines: Boundaries of the sarcomere. A band: Dark band, contains thick myosin filaments. I band: Light band, contains thin actin filaments. H zone: Central region of the A band, contains only myosin. M line: Center of the H zone, anchors myosin.
Membrane System:
Sarcolemma: Cell membrane. T-tubules: Invaginations of the sarcolemma. Sarcoplasmic Reticulum: Stores calcium ions.
Proteins:
Actin: Thin filaments. Myosin: Thick filaments. Troponin and Tropomyosin: Regulatory proteins on actin.
In summary, the ultrastructure of skeletal muscle is highly organized to facilitate contraction via the sliding filament mechanism.
10. Explain the sliding filament model of muscle contraction.
Answer: The sliding filament model explains how muscles contract at the molecular level.
Steps:
1. Excitation: A nerve impulse stimulates the muscle fiber, releasing calcium ions (Ca²⁺) from the sarcoplasmic reticulum.
2. Calcium Binding: Ca²⁺ binds to troponin on the thin actin filaments. This causes tropomyosin to move, exposing the myosin-binding sites on actin.
3. Cross-Bridge Formation: The myosin heads (thick filaments) bind to the exposed sites on actin, forming cross-bridges.
4. Power Stroke: The myosin heads pivot, pulling the actin filaments toward the center of the sarcomere. This requires ATP.
5. Cross-Bridge Detachment: ATP binds to myosin, causing it to detach from actin.
6. Re-cocking: The myosin head is re-energized by ATP hydrolysis, returning to its original position.
7. Cycle Repetition: The cycle repeats as long as Ca²⁺ and ATP are available.
Result: The thin filaments slide over the thick filaments, causing the sarcomere to shorten. This shortens the entire muscle fiber, producing contraction. The A band remains constant, while the I band and H zone shorten.
In summary, muscle contraction occurs by the sliding of actin filaments over myosin filaments, driven by ATP and regulated by calcium.
11. Explain the action of antagonistic muscles in the movement of knee joint in man.
Answer: The knee joint is a hinge joint that allows flexion and extension. Movement at the knee is controlled by antagonistic muscles.
Agonist (Prime Mover):
Quadriceps Femoris: Located on the front of the thigh. It is the agonist for knee extension. When it contracts, it straightens the leg.
Antagonist:
Hamstrings: Located on the back of the thigh. It is the antagonist for knee extension and the agonist for knee flexion. When it contracts, it bends the leg.
Movement:
Extension: The quadriceps contract, pulling the tibia forward and straightening the knee. The hamstrings relax. Flexion: The hamstrings contract, pulling the tibia backward and bending the knee. The quadriceps relax.
Coordination: The nervous system coordinates the contraction and relaxation of these opposing muscle groups to produce smooth, controlled movement.
In summary, antagonistic muscles (quadriceps and hamstrings) work in opposition to produce flexion and extension at the knee joint.
