Comprehensive Study Notes: Skeletal, Muscular, and Surface Anatomy (Chapters 5–12)

Chapter 5: Osseous Tissue and Skeletal Structure

Primary Functions of the Skeletal System

• Support: Provides structural framework for the body.

• Protection: Shields vital organs (e.g., skull protects brain, ribs protect heart and lungs).

• Leverage: Acts as levers for muscle action, enabling movement.

• Mineral Storage: Reservoir for minerals, especially calcium and phosphate.

• Blood Cell Production: Houses red bone marrow, site of hematopoiesis.

Tissues in the Skeletal System

• Bone (Osseous) Tissue

• Cartilage

• Ligaments

• Other Connective Tissues (e.g., periosteum, endosteum)

Bone Markings (General)

• Process: Projection or bump.

• Ramus: Extension of a bone making an angle with the rest of the structure.

• Trochanter: Large, rough projection (femur).

• Tuberosity: Smaller, rough projection.

• Tubercle: Small, rounded projection.

• Spine/Spinous: Pointed process.

• Head: Expanded articular end of an epiphysis.

• Neck: Narrow connection between head and diaphysis.

• Condyle: Smooth, rounded articular process.

• Facet: Small, flat articular surface.

• Fossa: Shallow depression.

• Foramen: Rounded passageway for blood vessels/nerves.

• Canal: Duct or channel.

• Sinus: Chamber within a bone, usually filled with air.

Types of Bone Shapes and Examples

• Long Bones: Longer than wide (e.g., femur, humerus).

• Short Bones: About equal in length and width (e.g., carpals, tarsals).

• Flat Bones: Thin, parallel surfaces (e.g., sternum, ribs, scapulae).

• Irregular Bones: Complex shapes (e.g., vertebrae, sphenoid).

• Sutural Bones: Small, flat, irregular bones between skull bones.

• Sesamoid Bones: Small, round, develop in tendons (e.g., patella).

Parts of a Long Bone

• Epiphysis: Expanded ends; contains spongy bone and red marrow.

• Metaphysis: Narrow region connecting epiphysis to diaphysis; site of growth plate.

• Diaphysis: Shaft; composed mainly of compact bone.

Bone Matrix Components

• Collagen Fibers: Provide tensile strength.

• Hydroxyapatite (Calcium Phosphate Crystals): Provide compressional strength.

Bone Cells and Functions

• Osteoblasts: Build new bone matrix (osteogenesis).

• Osteoclasts: Break down bone matrix (osteolysis).

• Osteocytes: Mature bone cells; maintain bone matrix.

Bone Matrix Homeostasis: Maintained by osteoblasts and osteoclasts.

Bone Remodeling

• Continuous process of bone resorption (by osteoclasts) and formation (by osteoblasts).

• Allows adaptation to stress and repair of microdamage.

Structure of Compact Bone

• Osteon (Haversian System): Structural unit; concentric lamellae around a central canal.

• Concentric Lamellae: Rings of bone matrix.

• Central Canal: Contains blood vessels and nerves.

• Perforating Canals: Connect central canals transversely.

• Lacunae: Small spaces housing osteocytes.

• Canaliculi: Tiny channels for nutrient/waste exchange between osteocytes.

Spongy Bone Structure and Function

• Composed of trabeculae; spaces filled with marrow.

• Reduces bone weight; supports and protects marrow.

Bone Marrow

• Red Marrow: Site of blood cell formation; found in spongy bone of flat bones and epiphyses.

• Yellow Marrow: Stores fat; found in medullary cavity of long bones.

Periosteum

• Dense connective tissue covering bone (except at joints).

• Contains osteoblasts, blood vessels, and nerves; essential for growth and repair.

Bone Ossification Types

• Endochondral Ossification: Bone replaces hyaline cartilage (most bones).

• Intramembranous Ossification: Bone develops from mesenchymal tissue (flat bones of skull, clavicle).

Regulation of Bone Remodeling

• Nutrition: Adequate calcium, vitamin D, and protein are essential.

• Hormones: Parathyroid hormone (PTH) increases blood calcium by stimulating osteoclasts; calcitonin lowers blood calcium by inhibiting osteoclasts.

• Exercise: Mechanical stress stimulates bone formation.

Fracture Healing Stages

1. Hematoma formation

2. Fibrocartilaginous callus formation

3. Bony callus formation

4. Bone remodeling

Types of Fractures

• Simple (closed), compound (open), comminuted, greenstick, spiral, transverse, oblique, etc.

Aging and Bone Structure

• Bone mass decreases; increased risk of osteoporosis and fractures.

Chapter 6: Axial Skeleton

Functions of the Axial Skeleton

• Supports and protects brain, spinal cord, and thoracic organs.

• Attachment for muscles of head, neck, and trunk.

Bones of the Orbit

• Frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal, ethmoid.

Hyoid Bone

• Located in anterior neck between mandible and larynx.

• Does not articulate with other bones; supports tongue and larynx.

Fontanelles

• Soft spots in infant skull; allow for brain growth and skull flexibility during birth.

Vertebral Column Regions

• Cervical: 7 vertebrae

• Thoracic: 12 vertebrae

• Lumbar: 5 vertebrae

• Sacral: 5 fused vertebrae

• Coccygeal: 3–5 fused vertebrae

Spinal Curves

• Cervical (secondary): Develops as infant holds head up.

• Thoracic (primary): Present at birth.

• Lumbar (secondary): Develops as child begins to walk.

• Sacral (primary): Present at birth.

Spinal Disorders

• Kyphosis: Exaggerated thoracic curve.

• Lordosis: Exaggerated lumbar curve.

• Scoliosis: Lateral curvature of the spine.

Ribs

• True Ribs (1–7): Attach directly to sternum.

• False Ribs (8–12): Attach indirectly or not at all.

• Floating Ribs (11–12): No anterior attachment.

Chapter 7: Appendicular Skeleton

Functions

• Movement and manipulation of objects; locomotion.

Major Bones

• Brachium: Humerus

• Antebrachium: Radius and ulna

• Pollex: Thumb

• Hallux: Big toe

• Thigh: Femur

• Leg: Tibia and fibula

Pelvic Differences

• Female pelvis: Wider, shallower, larger pelvic inlet/outlet for childbirth.

• Male pelvis: Narrower, deeper, more robust.

Aging and the Skeleton

• Bone mass and density decrease; joints may become less flexible.

Chapter 8: Articulations

Definition and Classification

• Articulation: Joint; where two bones meet.

• Range of Motion vs. Strength: Inverse relationship; more mobility means less stability.

Functional Classifications

• Synarthrosis: Immovable (e.g., sutures of skull).

• Amphiarthrosis: Slightly movable (e.g., pubic symphysis).

• Diarthrosis: Freely movable (e.g., shoulder, knee).

Structural Classifications

• Fibrous: Bones joined by fibrous tissue (e.g., sutures).

• Cartilaginous: Bones joined by cartilage (e.g., intervertebral discs).

• Bony: Fused bones (e.g., epiphyseal lines).

• Synovial: Joint cavity with synovial fluid (e.g., knee, elbow).

Synarthroses Types

• Suture, gomphosis, synchondrosis, synostosis

Amphiarthroses Types

• Syndesmosis, symphysis

Diarthroses (Synovial Joints) Structures

• Synovial membrane, synovial fluid, articular cartilage, articular capsule, fat pads, ligaments, tendons, bursae

Joint Stabilization

• Ligaments, tendons, articular capsule, muscle tone, menisci, labra

Types of Joint Movement

• Gliding, angular, rotation

Angular Movements

• Flexion, extension, hyperextension, abduction, adduction, circumduction

Rotational Movements

• Pronation, supination

Synovial Joint Shapes and Examples

• Gliding (carpals), hinge (elbow), pivot (atlas/axis), condylar (wrist), saddle (thumb), ball-and-socket (shoulder, hip)

Intervertebral Discs

• Annulus fibrosus (outer), nucleus pulposus (inner)

Disc Disorders

• Slipped (bulging) disc: Nucleus pulposus bulges but does not rupture annulus fibrosus.

• Herniated disc: Nucleus pulposus breaks through annulus fibrosus.

Joint Stability Comparisons

• Shoulder: More mobile, less stable.

• Elbow: Less mobile, more stable.

• Hip: Both mobile and stable due to deep socket, strong ligaments, and muscle support.

Knee Joint Structures

Ligaments	Cartilages	Tendon
Anterior cruciate ligament (ACL) Posterior cruciate ligament (PCL) Medial collateral ligament (MCL) Lateral collateral ligament (LCL) Patellar ligament	Medial meniscus Lateral meniscus	Quadriceps tendon

Degenerative Joint Changes

• Osteoarthritis, decreased synovial fluid, cartilage thinning

Chapter 9: Skeletal Muscle Tissue and Muscle Organization

Types of Muscle Tissue

• Skeletal (voluntary, striated)

• Cardiac (involuntary, striated)

• Smooth (involuntary, non-striated)

Functions of Skeletal Muscle

• Produce movement

• Maintain posture

• Support soft tissues

• Guard body openings

• Maintain body temperature

Connective Tissue Layers

• Epimysium: Surrounds entire muscle

• Perimysium: Surrounds fascicles

• Endomysium: Surrounds individual muscle fibers

• These combine to form tendons or aponeuroses

Skeletal Muscle Cell (Fiber)

• Large, multinucleated, formed by fusion of myoblasts

• Contains many myofibrils (contractile elements)

Membranes and Structures

• Sarcolemma: Plasma membrane of muscle fiber; continuous with T tubules

• Sarcoplasmic Reticulum (SR): Stores and releases Ca2+ for contraction

Sarcomere Structure

• Functional unit of contraction

• Contains thick (myosin) and thin (actin) filaments, Z line, M line, A band, I band, zone of overlap

Muscle Contraction: Key Ions and Events

• Ca2+ is essential; binds to troponin, exposing actin sites

• Cross-bridge: Myosin head binds to actin

Order of Events in Muscle Contraction

1. Action potential travels down axon of motor neuron

2. Release of acetylcholine from synaptic terminal

3. Acetylcholine binds to receptors on sarcolemma

4. Depolarization of sarcolemma and T tubules

5. Release of Ca2+ from SR

6. Ca2+ binds to troponin

7. Exposing of active sites on actin

8. Formation of cross-bridges

9. Power stroke

10. ATP causes cross-bridges to break

11. Myosin heads reactivated

Motor Units

• One motor neuron and all muscle fibers it innervates

• Arranged for fine or gross control

Muscle Fiber Types

• Fast (Type II): Quick, powerful, fatigue rapidly

• Intermediate: Properties between fast and slow

• Slow (Type I): Endurance, fatigue-resistant

Exercise Effects

• Increases muscle tone and size (hypertrophy); inactivity leads to atrophy

Fascicle Arrangements

• Parallel, convergent, pennate, circular

Muscle Attachments

• Origin: Fixed attachment

• Insertion: Movable attachment

Muscle Actions

• Prime mover (agonist): Main muscle causing movement

• Antagonist: Opposes prime mover

• Synergist: Assists prime mover

• Fixator: Stabilizes origin

Muscle Naming

• Position, number of tendons, shape, size, action, body region

Chapter 10: Axial Muscles

Functions

• Support and move head, neck, vertebral column; aid in breathing and abdominal wall movement

Key Axial Muscles

• Masseter, temporalis: Elevate mandible (chewing)

• Erector spinae: Extend vertebral column

• Spinal flexors: Flex vertebral column

• Intercostals: Move ribs for breathing

• Rectus abdominis: Flexes vertebral column

• Obliques, transversus abdominis: Compress abdomen, rotate trunk

• Diaphragm: Main muscle of respiration

Chapter 11: Appendicular Muscles

Functions

• Move and stabilize limbs

Key Appendicular Muscles

• Deltoid: Abducts arm

• Biceps brachii: Flexes elbow, supinates forearm

• Triceps brachii: Extends elbow

• Rotator cuff (supraspinatus, subscapularis, infraspinatus, teres minor): Stabilize shoulder

• Gluteal muscles: Extend, abduct thigh

• Adductors: Adduct thigh

• Hamstrings: Flex knee, extend hip

• Quadriceps: Extend knee

• Gastrocnemius, soleus: Plantarflex foot

Muscles in Fingers

• No intrinsic muscles in fingers; movement controlled by muscles in forearm (extrinsic hand muscles)

Aging and Muscular System

• Muscle mass and strength decrease; can be delayed by regular exercise

Chapter 12: Surface Anatomy

Prominent Skeletal Landmarks and Muscle Contours

Region	Landmarks/Muscles
Head	Supraorbital margin, mental protuberance, body of mandible, zygomatic bone, angle of mandible, mastoid process
Neck	Suprasternal notch, trapezius, sternocleidomastoid, thyroid cartilage, cervical triangles
Thoracic (anterior)	Clavicle, acromion, manubrium, sternum, xiphoid process, costal margin, pectoralis major, areola, nipple, axilla
Thoracic (posterior)	Vertebra C7, spine of scapula, vertebral border of scapula, inferior angle of scapula, trapezius, latissimus dorsi
Abdominal (anterior)	Rectus abdominis, serratus anterior, external oblique, umbilicus, tendinous inscriptions
Arm/Forearm	Biceps brachii, triceps brachii, deltoid, medial epicondyle of humerus, flexors/extensors of forearm, styloid process of ulna
Thigh/Leg	Iliac crest, quadriceps, hamstrings, tibial tuberosity, lateral malleolus of fibula, gastrocnemius

Example: The deltoid muscle forms the rounded contour of the shoulder and is easily palpable during arm abduction.

Additional info: These notes expand on the study guide by providing definitions, examples, and context for each topic, ensuring a comprehensive review for exam preparation.