A&P Concept Review: Biological Foundations, Skeletal System, and Nervous System

Flashcards derived from lecture notes covering key terms and concepts across homeostasis, biological macromolecules, tissue classifications, bone histology, skeletal growth and remodeling, blood calcium regulation, and nervous system anatomy and glial histology.

Homeostasis

The process of maintaining stable internal conditions within the body.

Positive Feedback

A homeostatic control mechanism in which the response amplifies the original stimulus and moves in the same direction as the stimulus.

Negative Feedback

A homeostatic control mechanism in which the response counteracts the original stimulus and works toward a set point.

Triglycerides

Lipids stored in adipose tissue that function in long-term energy storage, existing as saturated (no double bonds) or unsaturated ($\ge 1$ double bond).

Lipogenesis

The metabolic process of creating and storing triglycerides.

Lipolysis

The metabolic process of breaking down triglycerides.

Phospholipids

Molecules consisting of a polar head and non-polar tails that form cell membranes and help regulate substance movement into and out of cells.

Steroids

Lipid molecules characterized by multiple carbon rings that primarily function in cell signaling (e.g., testosterone, estrogen, cholesterol).

Monosaccharide

A single sugar unit, such as glucose or fructose.

Disaccharide

A carbohydrate formed from two monosaccharides bonded together, such as lactose.

Polysaccharide

A carbohydrate composed of many linked monosaccharide units, such as starch or chitin.

Glycogen

The stored form of carbohydrate energy in the body consisting of linked glucose molecules.

Adenosine Triphosphate (ATP)

The primary usable form of cellular energy, consisting of adenine, ribose, and $3$ phosphate groups.

Simple Diffusion

A passive movement of molecules directly through the cell membrane down a concentration gradient without requiring energy.

Osmosis

The passive movement of water down its concentration gradient across a membrane without energy expenditure.

Primary Active Transport

An active process that directly uses ATP to pump substances (such as $\text{Na}^+$, $\text{K}^+$, $\text{Ca}^{2+}$, or $\text{H}^+$) against their concentration gradient.

Secondary Active Transport

An active transport mechanism that does not directly use ATP, but uses energy from another substance moving down its concentration gradient to move a molecule.

Symport

A membrane transport process where two substances are moved in the same direction.

Antiport

A membrane transport process where two substances are moved in opposite directions.

Exocytosis

A bulk vesicular transport process that moves material out of the cell.

Endocytosis

A bulk vesicular transport process that moves material into the cell.

Epithelial Tissue

A tissue type characterized by tightly packed cells with little to no extracellular matrix and direct blood supply, forming protective barriers and linings.

Connective Tissue

The most common and diverse tissue type, characterized by specific cell types separated by a substantial extracellular matrix.

Compact Bone

Dense bone tissue that makes up about $80\%$ of skeletal mass and has the osteon as its functional unit.

Spongy Bone

Lightweight bone tissue that makes up about $20\%$ of skeletal mass and has the trabecula as its functional unit.

Hyaline Cartilage

The most common type of cartilage in the body, providing support while allowing flexibility and serving as the skeletal model during embryonic development.

Fibrocartilage

A very strong cartilage type containing collagen fibers that provides support and resistance to compression.

Ligaments

Dense regular connective tissue structures that connect bone to bone and stabilize joints.

Tendons

Dense regular connective tissue structures that connect muscle to bone to transmit muscle force.

Diaphysis

The central shaft region of a long bone, composed primarily of compact bone to provide strength.

Medullary Cavity

The hollow cavity inside the diaphysis of a long bone containing bone marrow.

Epiphysis

The expanded end of a long bone, composed primarily of spongy bone.

Metaphysis

The region between the diaphysis and epiphysis containing the growth plate in developing long bones.

Periosteum

The outer connective tissue covering of bone, anchored by perforating fibers, that contains blood vessels, nerves, and cells for bone growth and remodeling.

Endosteum

The tissue layer lining the internal surface of bone cavities, containing osteoblasts and osteoprogenitor cells.

Diploë

The layer of spongy bone located between inner and outer layers of compact bone in flat bones.

Red Bone Marrow

Myeloid tissue containing hematopoietic cells responsible for producing red blood cells, white blood cells, and platelets.

Yellow Bone Marrow

Bone marrow dominated by fat cells, utilized primarily for energy storage.

Osteoprogenitor Cells

Bone stem cells derived from mesenchyme that divide and differentiate into osteoblasts.

Osteoblasts

Bone-building cells that synthesize and secrete osteoid to initiate calcification.

Osteocytes

Mature bone cells trapped in lacunae that maintain the bone matrix and sense mechanical stress.

Osteoclasts

Large phagocytic cells that resorb and break down bone tissue.

Osteoid

The organic component of bone extracellular matrix, produced by osteoblasts and composed mainly of collagen and proteoglycans.

Osteon

The microscopic structural and functional unit of compact bone.

Central Canal

The longitudinal opening at the center of an osteon containing blood vessels and nerves.

Canaliculi

Tiny channels connecting lacunae that allow osteocytes to communicate and exchange nutrients and waste.

Perforating Canals

Transverse channels (Volkmann canals) that connect central canals with each other and carry blood vessels and nerves through bone.

Trabeculae

The lattice-like structural units of spongy bone that resist stress while keeping bone lightweight.

Chondroblasts

Immature cartilage cells that actively produce new cartilage matrix.

Chondrocytes

Mature cartilage cells that occupy lacunae and maintain the surrounding cartilage matrix.

Interstitial Growth

Growth in length that occurs from within a tissue, such as chondrocyte division within cartilage.

Appositional Growth

Growth in width or thickness that occurs along the outer surface or perimeter of bone or cartilage.

Intramembranous Ossification

Bone development directly from mesenchyme without using a cartilage model, forming flat bones of the skull and facial bones.

Endochondral Ossification

Bone development that begins with a hyaline cartilage model, forming most bones of the skeleton, including long bones.

Epiphyseal Plate

A layer of hyaline cartilage in the metaphysis where interstitial growth of long bones takes place.

Growth Hormone

A peptide hormone (somatotropin) produced by the anterior pituitary gland that stimulates chondrocyte cell division in the epiphyseal plate.

Calcitriol

The active hormone form of vitamin D that promotes calcium absorption from the small intestine into the blood.

Parathyroid Hormone (PTH)

A hormone released by parathyroid glands when blood calcium drops, acting to increase blood calcium levels by stimulating osteoclasts and decreasing renal calcium excretion.

Osteopenia

The normal, age-related loss of bone mass that typically begins around age $40$.

Osteoporosis

A severe medical condition characterized by substantial bone mass loss, increased porosity, and high fracture susceptibility.

Stress Fracture

A hairline crack in a bone caused by excessive or repeated mechanical stress.

Pathologic Fracture

A bone break caused by underlying disease or structural weakening, such as osteoporosis.

Simple Fracture

A bone fracture in which the broken bone does not pierce the skin.

Compound Fracture

A bone fracture in which the broken bone breaks through the surrounding skin.

Central Nervous System (CNS)

The structural division of the nervous system comprising the brain and spinal cord, acting as the primary site of integration and processing.

Peripheral Nervous System (PNS)

The structural division of the nervous system comprising nerves and ganglia that connects the CNS to the rest of the body.

Somatic Sensory System

The functional sensory division that transmits consciously perceived sensory input (e.g., touch, pain, temperature) to the CNS.

Visceral Sensory System

The functional sensory division that transmits input from internal organs, which is largely not consciously perceived.

Somatic Motor System

The motor division under conscious control that sends motor signals to skeletal muscles.

Autonomic Motor System

The involuntary motor division that sends commands to cardiac muscle, smooth muscle, and glands.

Nerve

A rope-like bundle of neuronal processes or axons located in the PNS, surrounded by connective tissue wrappings.

Ganglion

A localized collection of neuron cell bodies situated within the PNS.

Epineurium

The outermost connective tissue layer surrounding an entire nerve.

Perineurium

The connective tissue layer that surrounds a fascicle (bundle of axons) within a nerve.

Endoneurium

The connective tissue layer that surrounds individual nerve fibers/axons.

Excitability

The neuronal property defined as the capacity to respond to various electrical, chemical, or physical stimuli.

Conductivity

The neuronal property defined as the capacity to propagate electrical signals along the plasma membrane.

Secretion

The neuronal property defined as the ability to release neurotransmitters from synaptic knobs to communicate with target cells.

Axon Hillock

The triangular region where the axon attaches to the cell body, serving as the initiation site for neuronal electrical signals.

Anterograde Transport

Axonal movement of materials away from the cell body toward the axon terminals.

Retrograde Transport

Axonal movement of materials from the axon terminals back toward the cell body.

Fast Axonal Transport

Axonal transport occurring at approximately $100\,\text{mm/day}$, using ATP, motor proteins, and microtubules to move vesicles and organelles anterograde or retrograde.

Slow Axonal Transport

Axonal transport occurring at approximately $0.1\,\text{mm/day}$ to $3\,\text{mm/day}$, primarily moving smaller cellular components in an anterograde direction.

Multipolar Neurons

Neurons with multiple dendrites and a single axon, representing the most common structural type.

Afferent Neurons

Sensory neurons that transmit signals toward the central nervous system.

Efferent Neurons

Motor neurons that transmit signals away from the central nervous system toward effectors.

Interneurons

Neurons located entirely within the CNS that integrate, process, and store information between sensory and motor pathways.

Electrical Synapse

A rapid synapse where presynaptic and postsynaptic cells are directly connected via gap junctions without synaptic delay.

Chemical Synapse

A synapse where neurotransmitters are released from a presynaptic neuron across a synaptic cleft to bind receptors on a postsynaptic cell.

Astrocyte

A star-shaped CNS glial cell that supports the blood-brain barrier, regulates CNS fluid environment, assists neuron development, and maintains synapses.

Ependymal Cells

CNS glial cells lining brain ventricles and the spinal cord central canal that produce and circulate cerebrospinal fluid (CSF).

Microglia

Phagocytic immune cells in the CNS that protect against pathogens and clear debris from damaged tissue.

Oligodendrocytes

CNS glial cells that extend processes to wrap and insulate segments of multiple axons with myelin.

Satellite Cells

PNS glial cells that surround and support neuron cell bodies within ganglia and regulate their local environment.

Schwann Cells

PNS glial cells (neurolemmocytes) that wrap around PNS axons to form single segments of myelin sheath and assist in axon regeneration.

CNS

CNS

PNS

PNS