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Questions and Answers
Which layer of the skin is responsible for binding the epidermis to the tissue below?
Which type of skin cancer is characterized by the proliferation of stratum basal cells?
What type of cartilage is most abundant and provides support and flexibility?
Which pigment is primarily responsible for the pinkish hue of the skin?
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What is a characteristic feature of second-degree burns?
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Which of the following glands produces earwax for protection?
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What distinguishes third-degree burns from first and second-degree burns?
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Which type of skeletal cartilage contains elastic fibers and is found in the external ear?
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Which type of bone shape is characterized as cube-shaped and found in the wrists and ankles?
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What does the 'D' in the ABCDE rule for melanoma indicate?
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Which type of bone is characterized by a complicated shape?
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What is the primary function of osteoclasts in bone tissue?
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Which part of a long bone is known as the shaft?
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How are capillaries in spongy bone supplied with nutrients?
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Which type of ossification involves the formation of bone from a fibrous membrane?
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What do the trabeculae in spongy bone align along?
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What is the function of the central (Haversian) canal in compact bone?
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What characterizes the bone matrix secreted by osteoblasts during ossification?
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What forms when vascularized mesenchyme condenses on the external face of the woven bone?
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Which bone fracture type results from excessive twisting forces applied to a bone?
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During endochondral ossification, what occurs after the cartilage in the center of the diaphysis calcifies?
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Which type of fracture is characterized by bone fragments being pressed inward, typically found in the skull?
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What type of bone persists internally and becomes red marrow during ossification?
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Which of the following is NOT a characteristic of a comminuted fracture?
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When does the epiphyseal plate ossify, according to the stages of bone development?
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What is the outcome of the formation of a woven bone collar during ossification?
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What is the primary distinction between synarthroses and diarthroses?
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Which type of joint is classified as an amphiarthrosis?
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What characterizes a synovial joint?
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Which of the following is true regarding fibrous joints?
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Which movement occurs when a limb moves away from the midline of the body?
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What type of cartilage is involved in synchondroses?
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Which type of joint allows only for flexion and extension?
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What is a characteristic feature of saddle joints?
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What type of joint is primarily characterized by short gliding movements?
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Which structure is responsible for holding teeth in their sockets?
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Study Notes
Structure of Skin
- Epidermis: Outermost layer, composed of keratinized stratified squamous epithelium. Contains sweat glands, oil glands, hair, and hair follicles.
- Dermis: Middle layer, binds the epidermis to underlying tissue. Contains blood vessels, nerves, and lymphatic vessels. Composed of two layers: papillary and reticular.
- Hypodermis: Deepest layer, composed primarily of adipose tissue.
Skin Protection
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Sweat glands: Produce sweat, which helps regulate body temperature and eliminate waste.
- Eccrine: Found on forehead, neck, back, palms, and soles.
- Apocrine: Found in axillary regions and groin.
- Ceruminous: Found in ears, produces earwax.
- Oil glands: Produce sebum, which waterproofs and softens skin and hair.
Skin Color
- Melanin: Yellow to reddish-brown to black pigment, responsible for dark skin tones. Protects against UV radiation.
- Carotene: Yellow to orange pigment found in carrots and other vegetables, accumulates in the palms and soles.
- Hemoglobin: Responsible for pink hue of skin, carries oxygen in the blood.
Melanoma
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ABCDE rule: A guide for recognizing potential melanoma.
- Asymmetry: The two sides of the pigmented area do not match.
- Border: Exhibits indentations.
- Color: Black, brown, tan, and sometimes red or blue.
- Diameter: Larger than 6 mm.
- Evolving: Any change in elevation, itching, scabbing, or bleeding.
Skin Cancers
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Basal cell carcinoma: Least malignant, most common.
- Affects stratum basal cells.
- Treated by surgical excision.
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Squamous cell carcinoma: Second most common.
- Affects keratinocytes in stratum spinosum.
- Treatable by radiation therapy or surgical removal.
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Melanoma: Most dangerous.
- Affects melanocytes.
- Highly metastatic and resistant to chemotherapy.
- Treated by wide surgical excision and immunotherapy.
Burns
- First degree: Damages only the epidermis. Characterized by redness, edema, and pain.
- Second degree: Damages the epidermis and upper dermis. Characterized by blisters and pain.
- Third degree: Damages the entire thickness of the skin. Characterized by a gray-white, cherry red, or black appearance. Nerve endings are destroyed, resulting in a lack of initial edema or pain. Skin grafting is often necessary.
Cartilage
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Skeletal cartilage: Avascular and lacks nerves. Matrix is firm but flexible.
- Contains chondrocytes within lacunae.
- Surrounded by perichondrium (dense connective tissue).
- Forms three types: hyaline, elastic, and fibrocartilage.
Types of Cartilage
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Hyaline cartilage: Most abundant type.
- Provides support, flexibility, and resilience.
- Found in the ribcage, nose, trachea, and articular surfaces of bones.
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Elastic cartilage: Similar to hyaline cartilage but contains elastic fibers.
- More flexible than hyaline cartilage.
- Found in the external ear and epiglottis.
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Fibrocartilage: Contains thick collagen fibers.
- Highly tensile and able to withstand compression.
- Found in intervertebral discs, menisci of the knee, and the pubic symphysis.
Bones of the Skeleton
- Axial skeleton: The central axis of the body. Includes the skull, vertebral column, ribs, and sternum.
- Appendicular skeleton: The limbs and their girdles. Includes the bones of the arms, legs, shoulders, and hips.
Bone shapes
- Long bones: Longer than they are wide. Examples: femur, humerus.
- Short bones: Cube-shaped bones. Examples: carpals, tarsals.
- Sesamoid bones: Small bones that form within tendons. Example: patella.
- Flat bones: Thin, flat, slightly curved. Examples: cranial bones, sternum.
- Irregular bones: Complicated shapes. Examples: vertebrae, hip bones.
Bone Functions
- Support: Provides framework for the body and protects soft organs.
- Protection: Shields vital organs, such as the brain, spinal cord, and heart.
- Movement: Serves as levers for muscle action.
- Mineral storage: Stores calcium and phosphorus.
- Blood cell formation: Hematopoiesis occurs in the bone marrow.
- Triglyceride storage: Fat is stores in bone cavities.
Microscopic Anatomy of Bone
- Osteogenic cells: Stem cells that produce osteoblasts.
- Osteoblasts: Bone-forming cells.
- Osteocytes: Mature bone cells, reside in lacunae.
- Osteoclasts: Cells that break down (resorb) bone matrix.
Compact Bone Anatomy
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Osteon: Basic structural unit of compact bone.
- Lamellae: Concentric rings of bone matrix.
- Central canal: Contains blood vessels, nerves, and lymphatic vessels.
- Perforating canals: Connect the central canals, allowing for communication between blood vessels.
- Lacunae: Small cavities containing osteocytes.
- Canaliculi: Tiny canals that connect lacunae to each other and the central canal.
Spongy Bone Anatomy
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Trabeculae: Interconnecting bony struts that align along lines of stress.
- Contains irregularly arranged lamellae, osteocytes, and canaliculi.
- Capillaries in the endosteum supply nutrients.
Structure of a Long Bone
- Diaphysis: Shaft of the bone, composed primarily of compact bone.
- Epiphyses: Ends of a long bone, composed of spongy bone.
- Epiphyseal plate: Growth plate, responsible for bone lengthening.
- Articular cartilage: Covers the epiphyses, providing a smooth surface for joint articulation.
Bone Formation
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Intramembranous ossification: Bone forms directly from fibrous connective tissue.
- Forms flat bones like cranial bones and clavicle.
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Endochondral ossification: Bone forms by replacing hyaline cartilage.
- Forms most bones of the skeleton, such as long bones.
Intramembranous Ossification Steps
- Ossification center appears: Mesenchymal cells differentiate into osteoblasts, forming an ossification center.
- Bone matrix (osteoid) is secreted: Osteoblasts secrete osteoid, which mineralizes.
- Woven bone and periosteum form: Trabeculae develop, forming spongy bone, and the periosteum condenses on the outer surface.
- Compact bone forms: Trabeculae thicken, forming a bone collar of compact bone.
Endochondral Ossification Steps
- Bone collar forms: A bone collar of compact bone develops around a hyaline cartilage model.
- Cartilage calcifies: Cartilage in the center of the diaphysis calcifies and creates cavities.
- Periosteal bud invades cavities: Spongy bone formation begins.
- Diaphysis elongates: A medullary cavity forms, and secondary ossification centers appear at the epiphyses.
- Epiphyses ossify: Hyaline cartilage remains only in the epiphyseal plates and articular cartilage.
Bone Fractures
- Comminuted: Bone fragments into three or more pieces.
- Compression: Bone is crushed.
- Spiral: Excessive twisting forces cause a ragged break.
- Epiphyseal: Epiphysis separates from diaphysis at the growth plate.
- Depressed: Portion of bone is pressed inward.
- Greenstick: Incomplete break with bending on one side.
Skull
- Cranium bones: 8 bones: frontal, parietal (2), temporal (2), occipital, sphenoid, ethmoid.
- Facial bones: 14 bones; nasal (2), maxilla (2), zygomatic (2), mandible, lacrimal (2), palatine (2), inferior nasal concha (2), vomer.
Joint Classifications
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Functional Classifications: Based on movement.
- Synarthroses: Immovable joints.
- Amphiarthroses: Slightly movable joints.
- Diarthroses: Freely movable joints.
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Structural Classifications: Based on the type of connective tissue that unites the bones.
- Fibrous: Bones connected by dense fibrous connective tissue.
- Cartilaginous: Bones connected by cartilage.
- Synovial: Characterized by a joint (synovial) cavity.
Fibrous Joints
- Sutures: Short interconnecting fibers, bone edges interlock. Found only in the skull.
- Syndesmoses: Bones connected by a ligament. Fibrous tissue is longer than sutures. Examples: distal tibiofibular joint.
- Gomphoses: Peg-in-socket joint. Examples: tooth in socket.
Cartilaginous Joints
- Synchondroses: Bones joined by hyaline cartilage. Examples: epiphyseal plates, costochondral joints.
- Symphyses: Bones joined by fibrocartilage. Examples: pubic symphysis, intervertebral discs.
Synovial Joints
- Articular cartilage: Hyaline cartilage covering the ends of bones.
- Joint (synovial) cavity: A small potential space that contains synovial fluid.
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Articular (joint) capsule:
- Outer fibrous capsule: Dense connective tissue that surrounds the joint.
- Inner synovial membrane: Secretes synovial fluid.
- Synovial fluid: Fluid that lubricates and nourishes articular cartilage.
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Ligaments: Connect bones to other bones.
- Capsular: Part of the fibrous capsule.
- Extracapsular: Outside of the joint capsule.
- Intracapsular: Deep to the capsule, covered by the synovial membrane.
Synovial Joint Types
- Nonaxial (Plane) joints: Short gliding movements. Examples: intercarpal joints.
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Uniaxial joints: Motion in one plane.
- Hinge joints: Flexion and extension. Examples: elbow, knee, ankle.
- Pivot joints: Rotation. Examples: proximal radioulnar joint, atlantoaxial joint.
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Biaxial joints: Motion in two planes.
- Condyloid (ellipsoidal) joints: Flexion, extension, abduction, adduction, and circumduction. Examples: metacarpophalangeal joints.
- Saddle joints: Similar to condyloid joints but allow more freedom of movement. Examples: carpometacarpal joint of the thumb.
- Multiaxial joints: Movement in all planes.
- Ball-and-socket joints: Examples: shoulder, hip joints.
Friction-Reducing Structures
- Bursae: Flattened sacs lined with synovial membrane, located where tendons pass over bone. Reduce friction.
- Tendon sheaths: Elongated bursae that surround tendons, reducing friction during movements.
Synovial Joint Movements
- Gliding: One bone surface glides or slips over another.
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Angular movements:
- Flexion: Decreases the angle of a joint.
- Extension: Increases the angle of a joint.
- Hyperextension: Excessive extension beyond normal range of movement.
- Abduction: Movement away from the midline.
- Adduction: Movement towards the midline.
- Circumduction: Circular movement that combines flexion, abduction, extension, and adduction.
- Rotation: Turning a bone around its long axis.
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Special movements:
- Supination: Turning the hand with the palm up.
- Pronation: Turning the hand with the palm down.
- Dorsiflexion: Lifting the foot up toward the shin.
- Plantar flexion: Pointing the toes down.
- Inversion: Sole of the foot turns medially.
- Eversion: Sole of the foot turns laterally.
- Protraction: Moving a body part forward.
- Retraction: Moving a body part backward.
- Elevation: Lifting a body part superiorly.
- Depression: Moving a body part inferiorly.
- Opposition: Movement of the thumb to touch the tips of other fingers.
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Description
Test your knowledge on the structure, layers, and functions of the skin. This quiz covers the epidermis, dermis, hypodermis, and various glands involved in skin protection and color. Understand the role of sweat and oil glands in maintaining skin health.
