A&P final #3

What is bone ECM composed of?

35% organic (collagen + ground substance/osteoid) and 65% inorganic calcium phosphate crystals.

What makes bone dynamic?

Remodeling occurs in response to stress or inactivity.

What are osteoblasts?

Bone‑building cells on outer surface; deposit bone by secreting organic ECM and trapping calcium.

What are osteocytes?

Mature bone cells in lacunae; mostly inactive but maintain bone.

What are osteoclasts?

Large multinucleated cells that resorb bone by secreting hydrogen ions and enzymes.

What is blood classified as?

A unique connective tissue with fluid ECM (plasma).

What are plasma proteins?

Small proteins with diverse functions, including transport and clotting.

What are erythrocytes?

Red blood cells that bind and transport oxygen.

What are leukocytes?

White blood cells that function in immunity.

What are platelets?

Cell fragments that play a major role in blood clotting.

What are muscle tissues specialized for?

Contraction; converting chemical energy of ATP into mechanical energy of movement.

What body functions result from muscle tissue contraction?

Walking, breathing, heartbeat, propulsion of substances through hollow organs.

What is the main component of muscle tissue?

Muscle cell (myocyte), which is excitable and responds to electrical or chemical stimulation.

What are the two forms of muscle cells based on myofilament arrangement?

Striated (alternating light/dark bands) and smooth (irregular bundles).

What is endomysium?

Small amount of ECM surrounding muscle tissue; helps hold muscle cells together.

What are the three types of muscle tissue?

Skeletal, cardiac, and smooth muscle.

Which muscle tissues are striated?

Skeletal and cardiac.

Which muscle tissue is non‑striated?

Smooth muscle.

What is skeletal muscle tissue?

Mostly attached to skeleton; contraction produces body movement; under voluntary control.

How are skeletal muscle fibers formed?

By fusion of embryonic myoblasts, creating long multinucleated cells.

What is cardiac muscle tissue?

Found only in heart; striated, involuntary; cells are short, branched, with one nucleus.

What are intercalated discs?

Specialized structures in cardiac muscle containing gap junctions and desmosomes for communication and strength.

What is smooth muscle tissue?

Non‑striated; cells are spindle‑shaped with one nucleus; involuntary; found in walls of hollow organs.

How do smooth muscle cells contract?

Myofilaments arranged irregularly; contractions are slower and sustained.

What is the main function of nervous tissue?

Generating, sending, and receiving electrical messages.

What are the two main cell types in nervous tissue?

Neurons and neuroglial cells.

What are neurons?

Excitable cells capable of generating and transmitting electrical signals.

What are the three main parts of a neuron?

Cell body (soma), dendrites, and axon.

What is the function of the neuron cell body (soma)?

Houses nucleus and organelles; integrates information.

What are dendrites?

Short, branching processes that receive signals from other cells.

What is the axon?

Long process that transmits signals to other cells.

What are neuroglial cells?

Supporting cells that anchor neurons, provide nutrients, insulate, and protect.

How do neurons communicate?

Through electrical impulses and chemical signals at synapses.

What makes neurons excitable?

Ability to respond to stimuli with electrical changes across plasma membrane.

What is the role of neuroglial cells in homeostasis?

Maintain environment around neurons, protect from damage, assist in repair.

What is the ECM of nervous tissue like?

Unique; contains very few fibers, mostly ground substance with specialized molecules.

What percentage of body weight does skin account for?

10–15%, making it the largest organ.

What are the two main components of the cutaneous membrane?

Epidermis and dermis.

What type of tissue is the epidermis?

Keratinized stratified squamous epithelium.

What type of tissue is the dermis composed of?

Loose connective tissue and dense irregular connective tissue.

What are accessory structures of the skin?

Sweat glands, sebaceous glands, hair, nails.

What are arrector pili muscles?

Small bands of smooth muscle attached to hair.

Is the epidermis vascular?

No, it is avascular; relies on diffusion from dermis.

What is the hypodermis?

Subcutaneous fat layer deep to dermis; anchors skin; not part of skin.

What are the main functions of the integumentary system?

Protection, sensation, thermoregulation, excretion, vitamin D synthesis.

How does the skin protect against mechanical trauma?

Keratinized epithelium provides durable, flexible surface.

How does the skin protect against pathogens?

Continuous barrier; immune cells destroy invaders.

What is the acid mantle?

Slightly acidic pH from sebaceous secretions that inhibits pathogen growth.

How does skin protect against UV radiation?

Absorbs UV before deeper tissues are damaged.

How does skin maintain water/electrolyte balance?

Secretes hydrophobic lipid chemicals that repel water and salts.

How does skin provide sensation?

Sensory receptors detect stimuli like heat, cold, pain.

What is thermoregulation?

Maintenance of stable internal temperature via feedback loops.

What detects temperature changes?

Thermoreceptors in skin and fluids.

What is the role of the hypothalamus in thermoregulation?

Acts as thermostat; processes input and triggers responses.

How does the body cool itself?

Sweating and cutaneous vasodilation.

How does the body conserve heat?

Vasoconstriction redirects blood to deeper tissues.

What is excretion in the skin?

Elimination of small amounts of waste and toxins.

How does skin contribute to vitamin D synthesis?

UV converts cholesterol precursor to cholecalciferol → calcitriol → calcium absorption.

What are keratinocytes?

Cells making up 95% of epidermis; produce keratin.

What are desmosomes?

Junctions linking keratinocytes for strength.

What is the stratum basale?

Deepest layer; stem cells; most active; vitamin D synthesis.

What is the stratum spinosum?

Thickest layer; metabolically active; close to blood supply.

What is the stratum granulosum?

3–5 layers; keratin granules and lipid secretion; waterproofing.

What is the stratum lucidum?

Clear layer of dead keratinocytes; only in thick skin.

What is the stratum corneum?

Outermost layer; dead, flattened keratinocytes; exfoliated.

How long is the keratinocyte life cycle?

40–50 days from basale to shedding at corneum.

What are dendritic (Langerhans) cells?

Immune phagocytes in stratum spinosum.

What are Merkel cells?

Sensory receptors in stratum basale for light touch.

What are melanocytes?

Cells in stratum basale producing melanin pigment.

What is thick skin?

Found on palms/soles; all 5 layers; thick corneum; no hair; many sweat glands.

What is thin skin?

Covers rest of body; 4 layers (no lucidum); thinner; has hair, sweat, sebaceous glands.

What is a callus?

Extra stratum corneum formed in response to pressure.

What are the two layers of the dermis?

Papillary and reticular layers.

What is the papillary layer?

Superficial; loose connective tissue; anchors epidermis.

What are dermal papillae?

Projections containing capillaries and tactile corpuscles.

What are tactile (Meissner) corpuscles?

Sensory receptors for light touch.

What is the reticular layer?

Deep; dense irregular connective tissue; collagen bundles.

What do collagen bundles in dermis do?

Strengthen dermis; resist trauma.

What do elastic fibers in dermis do?

Allow skin to return to shape after stretching.

What are lamellated (Pacinian) corpuscles?

Pressure and vibration receptors in reticular layer.

What are dermal ridges?

Thick collagen areas forming epidermal ridges (fingerprints).

What are tension lines?

Skin markings from collagen gaps; cleavage lines.

What are flexure lines?

Deep creases where dermis is anchored to joints.

What pigment primarily determines skin color?

Melanin.

What enzyme catalyzes melanin production?

Tyrosinase.

What is the primary function of melanin?

Protect keratinocyte DNA from UV mutations.

How is melanin transferred to keratinocytes?

Via melanocyte extensions and melanosomes.

What is tanning?

Darkening of skin due to UV exposure; immediate oxidation + delayed increased production.

What is the secondary function of melanin?

Reduces vitamin D synthesis to regulate calcium absorption.

Why do populations in high UV regions have darker skin?

To prevent excess vitamin D production.

Why do populations in low UV regions have lighter skin?

To allow sufficient vitamin D synthesis.

Do people differ in melanocyte numbers?

No, numbers are similar; differences are in activity and melanin type.

What is a freckle?

Local area of increased melanin production.

What is a mole (nevus)?

Local proliferation of melanocytes.

What is albinism?

Genetic lack of tyrosinase; no melanin; high UV damage risk.

What is carotene?

Yellow‑orange pigment from diet; accumulates in stratum corneum.

What is hemoglobin’s role in skin color?

Oxygenated hemoglobin gives blood bright red color visible through skin.

What is erythema?

Increased blood flow in dermis; skin appears reddish; normal in exercise, fever, trauma, infection.

What is pallor?

Decreased blood flow in dermis; skin looks pale/whitish; occurs in cold or stress responses.

What is cyanosis?

Low oxygen in hemoglobin; blood turns reddish‑purple; skin appears bluish; indicates urgent medical issue.