Chapter 7: Bones and Bone Tissue

Classification of Bones by Shape and Location

• Long bones: Longer than they are wide (e.g., femur, humerus). Function in support and movement.

• Short bones: Nearly equal in length and width (e.g., carpals, tarsals). Provide stability and support.

• Flat bones: Thin, often curved (e.g., sternum, ribs, skull bones). Protect internal organs and provide surfaces for muscle attachment.

• Irregular bones: Complex shapes (e.g., vertebrae, some facial bones).

• Sesamoid bones: Embedded within tendons (e.g., patella).

Bone Cells and Their Functions

• Osteogenic cells: Stem cells that differentiate into osteoblasts.

• Osteoblasts: Bone-forming cells; synthesize osteoid and initiate mineralization.

• Osteocytes: Mature bone cells derived from osteoblasts; maintain bone matrix.

• Osteoclasts: Large, multinucleated cells that resorb (break down) bone matrix.

Bone Matrix: Osteoid vs. Hydroxyapatite

• Osteoid: Organic component of bone matrix, mainly collagen fibers; provides tensile strength and flexibility.

• Hydroxyapatite: Inorganic mineral component (); provides hardness and compressive strength.

Macroscopic Anatomy of Bones

• Periosteum: Dense connective tissue covering the outer surface of bone; contains nerves and blood vessels.

• Endosteum: Thin membrane lining the medullary cavity.

• Diaphysis: Shaft of a long bone.

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

• Articular cartilage: Hyaline cartilage covering joint surfaces; reduces friction.

• Yellow marrow: Stores fat; found in medullary cavity of adults.

• Red marrow: Site of hematopoiesis; found in spongy bone of certain bones.

• Perforating fibers (Sharpey's fibers): Anchor periosteum to bone.

• Compact bone: Dense outer layer; provides strength.

• Spongy bone (cancellous bone): Lattice-like structure; contains red marrow.

Microscopic Anatomy of Bones

• Osteon (Haversian system): Structural unit of compact bone; consists of concentric lamellae around a central canal.

• Central canal (Haversian canal): Contains blood vessels and nerves.

• Lacuna: Small spaces housing osteocytes.

• Trabeculae: Struts of spongy bone; align along lines of stress.

• Lamellae: Layers of bone matrix.

• Osteocyte: Mature bone cell within lacuna.

Calcium Homeostasis: Hormonal Regulation

• Calcitriol (active vitamin D): Increases blood calcium by promoting intestinal absorption.

• Parathyroid hormone (PTH): Increases blood calcium by stimulating osteoclasts and increasing renal reabsorption.

• Calcitonin: Lowers blood calcium by inhibiting osteoclasts and stimulating calcium deposition in bone.

Bone Formation: Ossification Types

• Endochondral ossification: Bone develops from hyaline cartilage (e.g., long bones).

• Intramembranous ossification: Bone develops directly from mesenchyme (e.g., flat bones of skull, clavicle).

Chapter 9: Joints and Articulations

Structural Classification of Joints

• Fibrous joints: Bones joined by dense connective tissue; little or no movement (e.g., sutures).

• Cartilaginous joints: Bones joined by cartilage (e.g., synchondroses, symphyses).

• Synovial joints: Bones separated by a joint cavity filled with synovial fluid; freely movable.

Functional Classification of Joints

• Synostosis: Immovable joint formed when bones fuse.

• Synarthrosis: Immovable joint (e.g., sutures).

• Amphiarthrosis: Slightly movable joint (e.g., intervertebral discs).

• Diarthrosis: Freely movable joint (e.g., synovial joints).

Structures of a Synovial Joint

• Joint cavity: Space containing synovial fluid.

• Synovial membrane: Produces synovial fluid for lubrication.

• Outer fibrous capsule: Encloses joint; provides stability.

• Articular disc: Pad of fibrocartilage; improves fit between bones.

• Meniscus: Crescent-shaped cartilage; absorbs shock.

• Bursa: Fluid-filled sac; reduces friction between structures.

Chapter 11: Muscular Tissue

Characteristics of Muscular Tissue

• Excitability: Ability to respond to stimuli.

• Contractility: Ability to shorten and generate force.

• Extensibility: Ability to stretch without damage.

• Elasticity: Ability to return to original length after stretching.

Types of Muscle Tissue

Muscle Structure: From Macro to Micro

• Epimysium: Surrounds entire muscle.

• Perimysium: Surrounds muscle fascicles (bundles of fibers).

• Endomysium: Surrounds individual muscle fibers.

• Fascicle: Bundle of muscle fibers.

• Muscle fiber: Single muscle cell.

• Myofibril: Rod-like unit within muscle fiber; contains myofilaments.

• Myofilament: Protein filaments (actin and myosin) responsible for contraction.

• Sarcolemma: Plasma membrane of muscle fiber.

• Sarcoplasm: Cytoplasm of muscle fiber.

• Sarcomere: Functional contractile unit; extends from Z disc to Z disc.

• A band: Dark region; contains thick filaments (myosin).

• I band: Light region; contains thin filaments (actin).

• H zone: Center of A band; only thick filaments.

• M line: Center of H zone; holds thick filaments together.

• Z disc: Boundary of sarcomere; anchors thin filaments.

• Actin: Thin filament protein.

• Myosin: Thick filament protein.

Muscle Contraction: Key Events and Structures

• Sarcoplasmic reticulum (SR): Stores and releases calcium ions.

• Transverse (T) tubules: Invaginations of sarcolemma; transmit action potentials.

• Terminal cisternae: Enlarged SR regions; release calcium.

• Triad: T tubule plus two terminal cisternae.

• Acetylcholine (ACh): Neurotransmitter at neuromuscular junction.

• Acetylcholinesterase: Enzyme that breaks down ACh.

• Calcium: Binds to troponin, initiating contraction.

• Troponin: Regulatory protein; binds calcium.

• Tropomyosin: Blocks myosin-binding sites on actin.

ATP Generation in Muscle Cells

• Creatine phosphate: Rapidly donates phosphate to ADP to form ATP; short-term energy.

• Anaerobic respiration: Produces ATP without oxygen; yields lactic acid.

• Aerobic respiration: Produces ATP using oxygen; yields more ATP per glucose.

Membrane Potentials in Muscle Cells

• Resting membrane potential: Baseline electrical charge across membrane.

• Depolarization: Membrane potential becomes less negative (more positive).

• Repolarization: Return to resting membrane potential.

• Hyperpolarization: Membrane potential becomes more negative than resting.

Chapter 12: Nervous Tissue

Central vs. Peripheral Nervous System

• Central nervous system (CNS): Brain and spinal cord; processes information.

• Peripheral nervous system (PNS): All neural tissue outside CNS; transmits signals to and from CNS.

Autonomic Nervous System: Sympathetic vs. Parasympathetic

• Sympathetic division: "Fight or flight"; increases heart rate, dilates pupils, inhibits digestion.

• Parasympathetic division: "Rest and digest"; decreases heart rate, stimulates digestion.

Neuronal Pathways and Terminology

• Afferent (sensory): Carry signals toward CNS.

• Efferent (motor): Carry signals away from CNS.

• Motor neurons: Transmit commands to muscles/glands.

• Sensory neurons: Transmit sensory information to CNS.

• Interneurons: Connect neurons within CNS; process information.

Graded vs. Action Potentials

• Graded potentials: Variable-strength signals; decrease with distance.

• Action potentials: All-or-none electrical impulses; propagate without decrement.

Factors Affecting Action Potential Conduction Velocity

• Axon diameter (larger = faster)

• Myelination (myelinated = faster)

• Temperature (higher = faster)

Temporal vs. Spatial Summation

• Temporal summation: Multiple signals from one neuron over time.

• Spatial summation: Multiple signals from different neurons at the same time.

Classes of Neurotransmitters and Their Functions

• Acetylcholine: Muscle contraction, autonomic functions.

• Glutamate: Main excitatory neurotransmitter in CNS.

• GABA: Main inhibitory neurotransmitter in CNS.

• Serotonin: Mood, appetite, sleep regulation.

• Norepinephrine/Epinephrine: Alertness, fight-or-flight response.

• Dopamine: Reward, motivation, motor control.

• Beta-endorphin: Reduces pain, produces euphoria.

Chapter 13: Spinal Cord, Spinal Nerves, Somatic Reflexes

Spinal Cord Anatomy

• Medullary cone (conus medullaris): Tapered end of spinal cord.

• Cauda equina: Bundle of spinal nerves below medullary cone.

• Terminal filum: Fibrous extension anchoring spinal cord.

• Cervical enlargement: Supplies nerves to upper limbs.

• Lumbosacral enlargement: Supplies nerves to lower limbs.

Information Flow in the Spinal Cord

• Dorsal horn: Receives sensory input.

• Ventral horn: Contains motor neurons.

• Lateral funiculus: White matter tract; carries signals.

• Dorsal/ventral rootlets: Small nerve fibers entering/exiting spinal cord.

• Anterior/posterior rami: Branches of spinal nerves; supply body regions.

Gray Matter vs. White Matter

• Gray matter: Neuron cell bodies; found in horns of spinal cord.

• White matter: Myelinated axons; found in funiculi (columns) surrounding gray matter.

Major Spinal Nerves and Plexuses

• Cervical plexus: Supplies neck, diaphragm (phrenic nerve).

• Brachial plexus: Supplies upper limb (e.g., radial, ulnar nerves).

• Lumbar plexus: Supplies anterior thigh (e.g., femoral nerve).

• Sacral plexus: Supplies posterior thigh, leg (e.g., sciatic nerve).

Reflex Arcs

• Monosynaptic: Single synapse (e.g., knee-jerk reflex).

• Polysynaptic: Multiple synapses (e.g., withdrawal reflex).

Chapter 14: Brain and Cranial Nerves

Major Brain Structures and Locations

• Frontal lobe: Anterior cerebrum; motor control, planning, speech.

• Temporal lobe: Lateral cerebrum; hearing, memory.

• Parietal lobe: Superior cerebrum; sensory processing.

• Occipital lobe: Posterior cerebrum; vision.

• Thalamus: Relay station for sensory information.

• Hypothalamus: Homeostasis, endocrine control.

• Pineal gland: Secretes melatonin; regulates circadian rhythms.

• Midbrain: Visual/auditory reflexes.

• Pons: Relays signals; regulates breathing.

• Medulla oblongata: Autonomic functions (heart rate, breathing).

• Cerebellum: Coordination, balance.

Cerebrospinal Fluid (CSF)

• Protects brain and spinal cord; provides nutrients; removes waste.

Meninges of the Brain and Spinal Cord

• Dura mater: Outermost, tough layer.

• Arachnoid mater: Middle, web-like layer.

• Pia mater: Innermost, delicate layer.

Cranial Nerves

• 12 pairs; numbered I-XII.

• Classified as sensory, motor, or both.

Chapter 15: The Autonomic Nervous System (ANS) & Visceral Reflexes

Autonomic Tone

• Baseline level of autonomic activity; allows for rapid adjustments.

Sympathetic vs. Parasympathetic Nervous System

• Sympathetic: Originates in thoracolumbar spinal cord; short preganglionic, long postganglionic fibers; releases norepinephrine (adrenergic) at target.

• Parasympathetic: Originates in craniosacral regions; long preganglionic, short postganglionic fibers; releases acetylcholine (cholinergic) at target.

Receptors and Their Effects

Comparison: ANS vs. Somatic Nervous System

• Somatic: Voluntary, single neuron to skeletal muscle, always excitatory.

• Autonomic: Involuntary, two-neuron chain to smooth/cardiac muscle or glands, excitatory or inhibitory.

Chapter 16: Sense Organs

Anatomy of the Ear

• Outer ear: Auricle (pinna), external auditory canal.

• Middle ear: Tympanic membrane, ossicles (malleus, incus, stapes).

• Inner ear: Cochlea, vestibule, semicircular canals.

Cochlea and Sound Transmission

• Scala vestibuli: Upper chamber; transmits sound vibrations.

• Scala tympani: Lower chamber; transmits sound vibrations.

• Scala media (cochlear duct): Contains organ of Corti.

• Vestibular membrane: Separates scala vestibuli and scala media.

• Basilar membrane: Supports organ of Corti; vibrates in response to sound.

• Tectorial membrane: Overlies hair cells in organ of Corti.

• Spiral organ (organ of Corti): Contains hair cells; site of auditory transduction.

• Hair cells: Sensory receptors for hearing.

Equilibrium: Static and Dynamic

• Static equilibrium: Detects head position relative to gravity (utricle, saccule).

• Dynamic equilibrium: Detects linear (utricle, saccule) and angular (semicircular canals) acceleration.

Anatomy of the Eye: The Three Tunics

• Fibrous tunic: Sclera and cornea.

• Vascular tunic: Choroid, ciliary body, iris.

• Nervous tunic: Retina.

Structures and Functions in Vision

• Sclera: White, protective outer layer.

• Cornea: Transparent, refracts light.

• Choroid: Vascular, nourishes retina.

• Ciliary bodies: Control lens shape.

• Iris: Regulates pupil size.

• Retina: Contains photoreceptors.

• Optic nerve: Transmits visual information to brain.

• Lens: Focuses light on retina.

• Aqueous humor: Fluid in anterior segment; nourishes lens/cornea.

• Vitreous humor: Gel in posterior segment; maintains eye shape.

• Macula lutea: Central region of retina; high acuity.

• Fovea centralis: Center of macula; sharpest vision.

• Optic disc: Blind spot; where optic nerve exits.

• Rods & rhodopsin: Low-light vision.

• Cones & photopsin: Color vision, high acuity.

• Bipolar cells: Transmit signals from photoreceptors to ganglion cells.

• Ganglion cells: Axons form optic nerve.

Additional info: Where content was brief or implied, academic context and definitions were added for completeness and clarity.