till week4

Stapes

The smallest bone in the human body, located in the middle ear.

Axial skeleton

The division of the skeletal system comprising the bones of the head, neck, and trunk.

Appendicular skeleton

The division of the skeletal system comprising the bones of the limbs, including the pectoral and pelvic girdles.

Bone Extracellular Matrix Composition

Consists of $45\%$ organic components ($30\%$ collagen and $15\%$ water) and $55\%$ crystallized mineral salts like Calcium Phosphate and calcium carbonate.

Compact bone

Dense bone that forms the outer shell of all bone, consisting of hollow pillars of bone matrix containing nerves and blood vessels.

Spongy bone (trabecular)

Bone composed of trabeculae aligned to assist with weight bearing; it is filled with red or yellow bone marrow.

Long bones

Bones that are longer than they are wide and bear a lot of weight, such as the femur and humerus.

Short bones

Cube-shaped bones with similar width and length that provide stability and support, such as carpal bones.

Sesamoid bones

A special type of short bone that is sesame-shaped and forms within a tendon.

Flat bones

Thin, flattened, and usually curved bones that protect vital organs and provide surfaces for muscle attachment, such as the sternum.

Irregular bones

Bones with complicated shapes that do not fit other categories, such as the vertebrae.

Diaphysis

The region of a long bone that forms the long axis.

Epiphysis

The proximal and distal ends of a long bone.

Metaphysis

The region between the epiphysis and diaphysis that contains the epiphyseal growth plate in growing bone.

Periosteum

A double-layered membrane and outer fibrous covering that covers the entire bone surface except for the joints.

Endosteum

A thin membrane that lines the medullary cavity, internal bone surfaces, trabeculae, and canals of compact bone.

Nutrient foramen

An opening at the center of the diaphysis through which the large nutrient artery enters the medullary cavity.

Osteoblasts

Bone-building cells that synthesize and secrete collagen fibers and organic components to build the extracellular matrix and initiate calcification.

Osteoclasts

Cells that break down the bone extracellular matrix ($\text{bone resorption}$) by releasing lysosomal enzymes and acids.

Intramembranous ossification

A process where bone forms directly from mesenchyme, typical for flat bones of the skull, facial bones, and the mandible.

Endochondral ossification

A process where bone replaces a cartilage model derived from mesenchyme, typical for long bones and the axial skeleton.

Interstitial growth

Growth in length occurring on the epiphyseal side of the epiphyseal plate.

Appositional growth

Bone growth in width or thickness where new bone is deposited on the outer surface while old bone lining the medullary cavity is destroyed.

Bone remodeling

The ongoing replacement of old bone tissue with new bone tissue, involving bone deposit by osteoblasts and bone resorption by osteoclasts.

Calcitriol

The active form of Vitamin D that increases calcium absorption in the body.

Foramen magnum

An opening in the occipital bone of the skull that serves as a passageway for the spinal cord.

Skeletal Muscle

Tissue that attaches to and covers the skeleton, providing voluntary contraction for overall body motility.

Cardiac Muscle

Muscle located only in the heart walls that is involuntary and composed of branching chains of cells with striations.

Smooth Muscle

Involuntary muscle present in the walls of hollow organs (e.g., stomach, trachea), characterized by single, fusiform, uninucleate cells without striations.

Electrical excitability

The property of muscular tissue that allows it to respond to stimuli to produce action potentials.

Contractility

The ability of muscle tissue to contract forcefully when stimulated.

Extensibility

The ability of muscle to stretch without being damaged, such as the stomach stretching with food.

Elasticity

The ability of muscle to return to its original length and shape after contraction and extension.

Epimysium

The connective tissue sheath that wraps an entire muscle, including individual muscle cells, blood vessels, and nerves.

Perimysium

The connective tissue wrapping that surrounds a fascicle, which is a bundle of individual muscle cells.

Endomysium

The connective tissue wrapping that surrounds an individual muscle fibre (muscle cell).

Circular arrangement

A pattern where fascicles are arranged into concentric rings, typically surrounding external body openings as sphincters (e.g., mouth).

Convergent arrangement

A pattern with a broad origin where fascicles converge toward a single tendon of insertion, providing the strongest contraction.

Parallel arrangement

A pattern where the length of fascicles runs parallel to the long axis of the muscle, allowing for the greatest shortening of length during contraction.

Pennate arrangement

A feather-like pattern where short fascicles attach obliquely to the tendon; includes unipennate, bipennate, and multipennate types.

Ligaments

Fibrous connections between bones composed of collagen fibres that usually blend with the periosteum at the joint.

Tendon

Fibrous tissue that links a muscle belly to its attachment site at a bone.

Aponeurosis

A broad, flat connective tissue that links a muscle belly to a site of attachment, spreading over a greater area than a tendon.

Raphe

A line of fibrous tissue where one muscle joins another; usually represents a long attachment.

Isometric contraction

A type of contraction that produces force with no change in muscle length, such as a plank.

Concentric contraction

A type of contraction that produces force by shortening the muscle length, such as in a barbell bicep curl.

Eccentric contraction

A type of contraction that produces force by lengthening the muscle, such as lowering a barbell from a bicep curl.

Prime mover (Agonist)

The main muscle responsible for producing a specific movement via concentric contraction.

Synergist

A muscle that complements the action of a prime mover by adding extra force or reducing unnecessary movements.

Antagonist

A muscle that opposes the action of another muscle via eccentric contraction and may regulate movement by providing resistance.

Fixator

A muscle that steadies proximal parts of a limb via isometric contraction while movements occur in distal parts (e.g., rotator cuff muscles).

Superficial fascia

Loose subcutaneous tissue that wraps, packages, and insulates deep structures.

Deep fascia

A thin, tough sheet primarily made of collagen fibres that is strong, inelastic, and found where expansion is not required.

Fascial septum

An extension of dense connective tissue, such as an intramuscular septum, that divides muscles into compartments.

Retinaculum

A thickening of deep fascia that serves to hold down tendons, such as the flexor retinaculum of the wrist.

Neurovascular hilum

The site near the center or belly of the muscle where the major source artery and vein enter.

Lymphatic system

A system comprised of lymph plexuses, vessels, nodes, and tissues that drains surplus tissue fluid and plasma proteins, and removes debris from cellular decomposition and infection.

Pulmonary circulation

The component of the cardiovascular system that carries O2 poor blood to the lungs for oxygenation.

Systemic circulation

The component of the cardiovascular system that carries O2 rich blood to the body for circulation.

Tunica intima

The innermost lining of blood vessel walls, consisting of flattened epithelial cells supported by delicate connective tissue.

Tunica media

The middle layer of blood vessel walls, composed mainly of smooth muscle, whose relative thickness differentiates arteries, veins, and lymphatic ducts.

Tunica adventitia

The outermost connective tissue layer or sheath of blood vessel walls.

Large elastic arteries

Conducting arteries located near the heart (such as the aorta) containing many elastic layers that ensure a smooth flow of blood.

Medium muscular arteries

Distributing arteries that make up the majority of named arteries; they contain circular smooth muscle fibres responsible for vasoconstriction and blood flow regulation.

Small arteries and arterioles

Vessels with narrow lumina and thick smooth muscle walls that flow into capillary beds and regulate arterial pressure through tonus.

Anastomoses

Links between adjacent arteries or arterioles that provide potential detours (collateral flow) for blood if the normal pathway is obstructed.

End arteries

Arteries that do not link or anastomose with other arteries, but instead branch directly into capillary beds drained by veins.

Venae comitantes

Paired or multiple deep veins that closely accompany an artery.

Venous valves

Folds of endothelium lining veins (usually consisting of a pair of cusps) that enforce unidirectional blood flow from distal to proximal.

Capillaries

Simple endothelial tubes consisting only of a tunica intima and basement membrane that connect arterioles and venules, allowing material exchange with interstitial fluid.

Vasomotor nerves

Visceral motor nerves, originating almost exclusively from the sympathetic nervous system, that modulate the continuous partial contraction (tone) of vascular smooth muscle.

Vascular venous pumps

Arrangements of venae comitantes within unyielding connective tissue where arterial pulsations compress veins and drive blood flow proximally via valves.

Musculovenous pump

The primary mechanism for venous return from the limbs, in which skeletal muscle expansion is constrained by fascia, causing muscle contraction to 'milk' blood superiorly.

Thoracic venous pump

A respiration-driven double pump mechanism in which diaphragm movement alters the lengths and filling dynamics of the IVC and SVC.

Lymph nodes

Filtered encapsulated structures traversed by lymph vessels that trap particulate, defend against foreign antigens, and slow lymph flow.

Right lymphatic duct and Thoracic duct

Major lymphatic ducts formed by the union of lymphatic trunks that drain lymph back into the venous system at the junction of the internal jugular and subclavian veins.

Epineurium

A common external connective tissue sheath that surrounds collections of thousands of individual axons to form a nerve.

Fascicles

Groups of axons within a nerve that are surrounded by a perineurial sheath.

Efferent axons

Motor axons that carry signals from the Central Nervous System (CNS) to the periphery.

Afferent axons

Sensory axons that carry signals from the periphery to the Central Nervous System (CNS).

Ganglia

A collection of neuron cell bodies located in the peripheral nervous system.

Dorsal (posterior) root

The structural pathway through which sensory (afferent) axons join the Central Nervous System.

Ventral (anterior) root

The structural pathway through which motor (efferent) axons join the Central Nervous System.

Cervical nerves

8 pairs of spinal nerves designated as $C1-C8$.

Thoracic nerves

12 pairs of spinal nerves designated as $T1-T12$.

Lumbar nerves

5 pairs of spinal nerves designated as $L1-L5$.

Sacral nerves

5 pairs of spinal nerves designated as $S1-S5$.

Coccygeal nerves

1 pair of spinal nerves designated as $Co1$.

Dermatome

An area of skin that is mainly supplied by a single spinal nerve.

Myotome

A group of muscles that is innervated by a single spinal nerve.

Nerve Plexus

A network where several spinal segments contribute axons to a single peripheral nerve, such as the Cervical, Brachial, or Lumbosacral plexuses.

Olfactory nerve (I)

A sensory cranial nerve responsible for the nose/smell.

Optic nerve (II)

A sensory cranial nerve responsible for the eye/vision.

Oculomotor nerve (III)

A motor cranial nerve that controls most eye muscles and narrows the pupil/focuses the lens.

Trochlear nerve (IV)

A motor cranial nerve that supplies the superior oblique muscle of the eye.

Trigeminal nerve (V)

A cranial nerve providing sensory input for the face, teeth, and sinuses, and motor control for the muscles of mastication.

Abducens nerve (VI)

A motor cranial nerve responsible for the external rectus muscle of the eye.

Facial nerve (VII)

A cranial nerve providing motor control to facial muscles and tear/salivary glands, and sensory input from the anterior tongue.

Vestibulocochlear nerve (VIII)

A sensory cranial nerve responsible for the inner ear (vestibular and cochlear functions).

Glossopharyngeal nerve (IX)

A cranial nerve providing motor control to the pharyngeal musculature and parotid gland, and sensory input from the posterior tongue.