A&P

Question: What are the four types of human tissues classified by structure and function? Answer: Epithelial tissue: Forms boundaries; Muscle tissue: Enables contraction; Nervous tissue: Facilitates communication and control; Connective tissue: Provides connection and support.

Question: What is epithelial tissue/epithelium? Answer: a sheet of cells that covers a body surface or lines a body cavity.

Question: How is epithelium classified by number of cell layers? Answer: 1 layer = simple; >1 layer = stratified.

Question: What are the three major epithelial cell shapes? Answer: Squamous: scalelike; Cuboidal: cubelike; Columnar: column-shaped.

Question: What general principle connects epithelial structure and function? Answer: Structure supports function.

Question: What is the first common function of epithelial tissue? Answer: Form barriers that separate the body from the external environment or divide bodily compartments with distinct physical or chemical properties.

Question: What does the skin do as an epithelial barrier? Answer: separates the internal from external environment.

Question: What does the endothelium of blood vessels do as an epithelial barrier? Answer: Acts as a barrier between the blood and the surrounding tissues of the body.

Question: What does the blood-brain barrier separate? Answer: the circulating blood from the brain’s extracellular fluid.

Question: What are four common functions of epithelial tissue? Answer: Form barriers, secretion, absorption, sensation.

Question: What is an example of secretion by epithelial tissue? Answer: sweat gland, sebaceous gland.

Question: What is an example of absorption by epithelial tissue? Answer: sweat gland duct.

Question: What is an example of sensation by epithelial tissue? Answer: Merkel cells.

Question: What do external boundaries do? Answer: separate the body from external environment.

Question: What do internal boundaries do? Answer: Separate one part of the body from another.

Question: What is an example of an internal boundary? Answer: Blood-Testis Barrier.

Question: What are exocrine glands? Answer: secretory epithelium surrounds a duct, which empties their secretion out of the body.

Question: What are examples of exocrine gland secretions? Answer: mucus, saliva, sweat, earwax, oils, and milk.

Question: What are endocrine glands? Answer: are ductless, they release their secretion (hormones) into the blood - circulatory system.

Question: What are examples of endocrine glands? Answer: pituitary gland, adrenal gland, and thyroid gland.

Question: What are glandular cells? Answer: specialized epithelial cells with secretory machinery.

Question: What are the characteristics of epithelial tissues? Answer: Polarity: apical vs basal; Specialized contacts: bound together by specialized junctions; Supported by connective tissue: basement membrane; Avascular but innervated; Regeneration.

Question: What does polarity mean in epithelial tissues? Answer: apical vs basal.

Question: What are specialized contacts in epithelial tissue? Answer: bound together by specialized junctions.

Question: How are epithelial tissues supported by connective tissue? Answer: basement membrane.

Question: What is the basement membrane? Answer: an acellular material secreted partly by the epithelial cells and connective tissue cells.

Question: What does avascular but innervated mean for epithelial tissue? Answer: depend on diffusion of nutrients from underlying connective tissue.

Question: What is the regenerative characteristic of epithelial tissue? Answer: epithelial cells can easily divide to regenerate the tissue.

Question: What is Common Structural Feature #1 of epithelial tissue? Answer: Various Cell Junctions Tighten the Packing of Epithelial Cells.

Question: What is the main function of tight junctions? Answer: Seal space between cells to prevent paracellular leakage.

Question: What are the key proteins of tight junctions? Answer: Claudins, occludins.

Question: Where are tight junctions typically distributed in epithelium? Answer: Apical region of absorptive epithelia (e.g., intestinal lining, kidney tubules) to maintain polarity.

Question: What is the main function of adherens junctions? Answer: Mechanical link between actin cytoskeletons of adjacent cells.

Question: What are the key proteins of adherens junctions? Answer: Cadherins (E-cadherin), catenins.

Question: Where are adherens junctions typically distributed in epithelium? Answer: Just below tight junctions in most simple epithelia (e.g., intestinal epithelium) to maintain tissue integrity.

Question: What is the main function of desmosomes? Answer: Strong spot-like adhesion, resist mechanical stress.

Question: What are the key proteins of desmosomes? Answer: Desmoglein, desmocollin (cadherins).

Question: Where are desmosomes abundant? Answer: stratified squamous epithelium (skin epidermis, esophagus).

Question: What is the main function of hemidesmosomes? Answer: Anchor basal surface of epithelial cells to basement membrane.

Question: What are the key proteins of hemidesmosomes? Answer: Integrins, BP180, BP230.

Question: Where are hemidesmosomes typically found? Answer: Basal surface of epidermis and other epithelia under mechanical stress.

Question: What is the main function of gap junctions? Answer: Direct communication via ion and small molecule exchange.

Question: What are the key proteins of gap junctions? Answer: Connexins.

Question: Where are gap junctions found in epithelia? Answer: Found in epithelia that coordinate activity, e.g., ciliated epithelium of respiratory tract, secretory epithelium of glands.

Question: What is Common Structural Feature #2 of epithelial tissue? Answer: Epithelial cells are polarized.

Question: What does the basal surface of an epithelial cell do? Answer: adheres to basement membrane (layers of extracellular matrix).

Question: What does the apical surface of an epithelial cell face? Answer: the lumen or external space.

Question: What is epithelial polarity? Answer: A structural and functional asymmetry exists within the cell.

Question: What specialized feature allows epithelial cells in the small intestine to absorb nutrients? Answer: Cells are equipped with specialized protein transporter that recognize and absorb various nutrients.

Question: What does apical-basal polarity accomplish in the small intestine? Answer: Protein machinery is localized to different surfaces, ensuring the proper execution of specific functions.

Question: How much do villi and microvilli increase intestinal surface area? Answer: Villi+Microvilli increase the surface area by ~600x compared to a smooth tube.

Question: What specialized feature allows epithelial cells in gastric glands to generate acid? Answer: Cells are equipped with specialized protein tools for generating acids and secretion.

Question: What does active metabolism in parietal cells generate? Answer: lots of CO2.

Question: What enzyme catalyzes the formation of carbonic acid? Answer: carbonic anhydrase.

Question: What does carbonic anhydrase catalyze? Answer: the formation of carbonic acid (H2CO3).

Question: What does carbonic acid immediately dissociate into? Answer: the bicarbonate ion (HCO3−) and a proton (H+).

Question: What happens to the protons generated in parietal cells? Answer: The protons are actively (using ATP) pumped into the stomach lumen.

Question: What happens to HCO3− in parietal cells? Answer: HCO3− is transported to blood in exchange for Cl− from the blood.

Question: What is the exchange of HCO3− for Cl− called? Answer: Chloride Shift.

Question: What happens to Cl− after entering a parietal cell? Answer: Cl− is then transported into the lumen via a Cl− channel.

Question: What is endothelium? Answer: Simple squamous epithelium lining the inner surface of blood vessel walls.

Question: What forms the entire vessel wall in capillaries? Answer: endothelium.

Question: How does endothelium regulate vascular tone? Answer: by releasing signaling molecules.

Question: What is angiogenesis? Answer: formation of new blood vessels.

Question: What are major functions of endothelium? Answer: Regulates vascular tone by releasing signaling molecules; involved in angiogenesis; facilitates immune cell trafficking; regulate blood clotting.

Question: What does endothelium do in capillaries? Answer: acts as a selective barrier between blood and tissues, allowing efficient exchange of gases, nutrients, and waste.

Question: What are continuous capillaries? Answer: Have tight junctions, forming a barrier as in the blood-brain barrier (BBB).

Question: Where are continuous capillaries found? Answer: brain, lungs.

Question: What are fenestrated capillaries? Answer: Have small pores within endothelial cells to allow greater permeability.

Question: Where are fenestrated capillaries found? Answer: kidneys, intestines.

Question: What are sinusoidal capillaries? Answer: Have large gaps between cells to allow the passage of larger molecules like proteins and cells.

Question: Where are sinusoidal capillaries found? Answer: liver, spleen.

Question: What are the structural characteristics of epithelial tissue in the epidermis? Answer: Avascular (lacking blood vessels or blood supply); Aneural (lacking nerves or nerve supply).

Question: What is the main function of epithelial tissue in the epidermis? Answer: Form barriers that separate the body from the external environment.

Question: What are the layers of the epidermis from superficial to deep? Answer: Stratum corneum; Stratum lucidum; Stratum granulosum; Stratum spinosum; Stratum basale.

Question: What characterizes the stratum corneum? Answer: 20-30 layers of dead keratinocytes, shedding.

Question: Where is the stratum lucidum found? Answer: thick skin only.

Question: What happens to keratinocytes in the stratum lucidum in response to mechanical stress? Answer: keratinocytes are genetically programmed to pass through an extra transitional stage.

Question: What is the stratum lucidum packed with? Answer: eleidin, a clear, lipid-rich form of keratin derived from keratohyalin granules.

Question: How many distinct keratins does human skin express? Answer: > 20 distinct keratins (37 genes), e.g., hair, nail, wound etc.

Question: What happens in the stratum granulosum? Answer: Accumulate lamellar granules & keratohyalin granules; Apoptosis occurs, cells become flat and die.

Question: What happens in the stratum spinosum? Answer: Start to produce keratin and release glycolipids.

Question: What connects cells tightly in the stratum spinosum? Answer: Desmosomes ("spines").

Question: What protection does the stratum spinosum provide? Answer: Provide protection against penetration by irritants and pathogens and loss of water.

Question: What occurs in the stratum basale? Answer: Mitotic division, stem cells.

Question: What are the key features of connective tissue? Answer: Consists of cells loosely scattered within a liquid, jellylike, or solid matrix.

Question: What determines a connective tissue's physical property? Answer: The nature of the matrix determines the tissue’s physical property.

Question: What do fibers provide to connective tissue? Answer: strength to the tissue.

Question: What does ground substance do in connective tissue? Answer: traps water and fills space between cells and fibers.

Question: Who usually secretes the connective tissue matrix? Answer: The matrix is usually secreted by the connective tissue cells themselves.

Question: What are the major components of connective tissue? Answer: Cells, fibers, ground substance.

Question: What proteins make up collagen fibers? Answer: collagen proteins.

Question: What proteins make up elastic fibers? Answer: elastin + fibrillin proteins.

Question: What proteins make up reticular fibers? Answer: collagen proteins.

Question: What are major components of connective tissue ground substance? Answer: Polysaccharides; Proteoglycans.

Question: What are the three groups of connective tissues? Answer: Connective Tissue Proper; Supportive Connective Tissue; Fluid Connective Tissue.

Question: What are the two major forms of connective tissue proper? Answer: Loose connective tissue and Dense connective tissue.

Question: What are the three forms of loose connective tissue? Answer: Areolar, adipose, reticular.

Question: Where is areolar connective tissue found? Answer: Skin, GI tract.

Question: Where is adipose connective tissue found? Answer: Fat, bone marrow.

Question: Where is reticular connective tissue found? Answer: Lymph node, liver.

Question: What are the three forms of dense connective tissue? Answer: Regular, irregular, elastic.

Question: Where is dense regular connective tissue found? Answer: tendons, ligaments.

Question: Where is dense irregular connective tissue found? Answer: skin.

Question: Where is elastic connective tissue found? Answer: aorta.

Question: What are the three types of cartilage? Answer: Hyaline, elastic, fibrocartilage.

Question: Where is hyaline cartilage found? Answer: synovial joints.

Question: Where is elastic cartilage found? Answer: external ear, epiglottis.

Question: Where is fibrocartilage found? Answer: Intervertebral discs, menisci of the knee joint.

Question: Is cartilage vascular or avascular? Answer: avascular.

Question: What are the two major structural forms of bone? Answer: Compact bone and spongy bone.

Question: Where is compact bone found? Answer: outer layer of bones.

Question: Where is spongy bone found? Answer: interiors of bones.

Question: What are the major cells of loose connective tissue? Answer: Fibroblasts.

Question: What fibers are found in loose connective tissue? Answer: Collagen Type III, IV, VI, XVIII & Elastic Fibers.

Question: What ground substance is found in loose connective tissue? Answer: Hyaluronic acid, proteoglycans, glycoproteins; High water content.

Question: What are the major cells of dense connective tissue? Answer: Fibroblasts.

Question: What collagen types are found in dense connective tissue? Answer: Collagen Type I, V, XII, XIV.

Question: What characterizes the ground substance of dense connective tissue? Answer: More proteoglycans; Less water, more fibrous proteins.

Question: What are the major cells of cartilage? Answer: Chondrocytes.

Question: What collagen fiber is characteristic of cartilage? Answer: Collagen type II Fibers.

Question: What makes up the ground substance of cartilage? Answer: Chondroitin sulfate, hyaluronic acid, and proteoglycans.

Question: What are the major cell types of bone? Answer: Osteoblasts, Osteocytes, Osteoclasts.

Question: What do osteoclasts do? Answer: breakdown bones.

Question: What collagen fiber is characteristic of bone? Answer: Collagen type I Fibers, Non-Collagenous Proteins.

Question: What makes up the ground substance of bone? Answer: Minerals (Ca10(PO4)6(OH)2), Proteoglycans & Glycoproteins.

Question: What are proteoglycans and glycoproteins? Answer: sugar modified proteins.

Question: What is chondroitin sulfate? Answer: repeated disaccharide units, sulfated at different positions for functional diversity.

Question: What is hyaluronic acid? Answer: repeated disaccharide units, unsulfured.

Question: What do these ground-substance components provide? Answer: strength, resilience, shock absorption, hydration & lubrication.

Question: What additional functions do these ground-substance components perform? Answer: cell adhesion and migration, wound healing, anti-inflammation.

Question: What are the major roles of connective tissue? Answer: Binding and connection; Support and cushioning; Storage; Insulation; Protection.

Question: What is the key physical property of loose connective tissue? Answer: Soft, flexible; provides cushioning and support.

Question: What is the key physical property of dense connective tissue? Answer: Strong and resistant to stretch; provides tensile strength and structural integrity.

Question: What is the key physical property of cartilage? Answer: Firm, semi-rigid; resilient and compressible; avascular; high water content in matrix.

Question: What is the key physical property of bone? Answer: Very hard; dense (compact) or porous (spongy); highly mineralized matrix; provide support and protection.

Question: What is the key physical property of blood? Answer: Fluid; plasma matrix allows free movement of cells and solutes.

Question: What is the key physical property of lymph? Answer: Clear, watery fluid; low in cells and protein; transports immune cells and interstitial fluid.

Question: What is tissue compatibility as a structural consideration of connective tissue? Answer: arranging multiple tissue types of different stiffness and stretchability in a seamless architecture.

Question: What is spatial arrangement as a structural consideration of connective tissue? Answer: Ensuring structures are positioned to support function (e.g., layering in skin, fiber orientation in muscle).

Question: What is mechanical support as a structural consideration of connective tissue? Answer: Providing durability and flexibility (e.g., connective tissue scaffolding).

Question: What is integration of input/output as a functional consideration of connective tissue? Answer: Connecting sensory inputs to processing centers and effectors (e.g., in skin: receptors → nerves → brain → sweat glands).

Question: How does connective tissue contribute to nutrient supply and waste removal? Answer: blood supply.

Question: How does connective tissue contribute to signal conduction? Answer: Positioning neurons and receptors for rapid and targeted communication.

Question: What is a general role of connective tissue in tissue organization? Answer: The art of packing and accommodating various tissues in 3D space and enable their functions and connectivity.

Question: What does the skin demonstrate about tissue organization? Answer: The Skin: Built from All Four Tissue Types.

Question: What are the epithelial tissue subtypes? Answer: Simple (squamous, cuboidal, columnar); Stratified (squamous, cuboidal, columnar); Pseudostratified; Transitional.

Question: What are the major functions of epithelial tissue? Answer: Protection (e.g. epidermis); Secretion (e.g. sweat glands, sebaceous glands); Absorption (e.g. sweat gland duct).

Question: What are the connective tissue subtypes? Answer: Loose (areolar, adipose, reticular); Dense (regular, irregular, elastic); Cartilage (hyaline, elastic, fibrocartilage); Bone; Blood, lymph.

Question: What are the major functions of connective tissue? Answer: Structural support; Binding tissues; Energy storage; Transport (blood, lymph); Immune defense (blood, lymph).

Question: What are the three muscle tissue subtypes? Answer: Skeletal; Cardiac; Smooth.

Question: What are the major functions of muscle tissue? Answer: Movement (voluntary and involuntary, e.g., arrector pili muscle); Heat generation; Pumping blood (cardiac).

Question: What are the nervous tissue subtypes? Answer: Neurons; Neuroglia (glial cells).

Question: What are the major functions of nervous tissue? Answer: Sensory input; Integration and processing; Motor output; Support and protection of neurons.

Question: What type of connective tissue forms the papillary layer of the dermis? Answer: Areolar connective tissue.

Question: What is the first function of dermal papillae? Answer: Increase area interfacing epidermis → strengthen the attachment with epidermis.

Question: What is the second function of dermal papillae? Answer: Increase friction and grip strength.

Question: What is the third function of dermal papillae? Answer: House touch receptors & pain receptors, e.g., Meissner’s corpuscles, free nerve endings.

Question: What vascular structures are associated with the papillary layer? Answer: Capillary loop; Subpapillary / superficial vascular plexus.

Question: What type of connective tissue forms the reticular layer? Answer: Dense irregular connective tissue.

Question: What is the function of dense irregular connective tissue in the reticular layer? Answer: provide strength; protect and support the embedded accessary organs.

Question: What vascular structure is associated with the reticular layer? Answer: Deep vascular plexus.

Question: What receptors are associated with the reticular layer? Answer: Ruffini corpuscle, lamellar corpuscle, etc.

Question: What do fibroblasts in the dermis do? Answer: maintain the matrix (fibers and ground substance).

Question: What do adipocytes do? Answer: energy storage and insulation.

Question: What do macrophages do? Answer: immune surveillance.

Question: What are the main cell types of areolar connective tissue in the papillary layer? Answer: Fibroblasts, WBCs.

Question: What fibers are present in areolar connective tissue? Answer: Loosely organized thin collagen, elastic, reticular; provides flexibility.

Question: What is the ground substance of areolar connective tissue like? Answer: Abundant, gel-like; allows fast diffusion and gentle support.

Question: What are the cells of adipose connective tissue? Answer: Adipocytes (fat cells).

Question: What fibers are found in adipose connective tissue? Answer: Sparse reticular fibers.

Question: What is the ground substance of adipose connective tissue like? Answer: Minimal; mostly filled with lipid-storing cells.

Question: What are the cells of reticular connective tissue? Answer: Reticular cells, WBCs.

Question: What fibers characterize reticular connective tissue? Answer: Reticular (thin, branching collagen III).

Question: What is the ground substance of reticular connective tissue like? Answer: Soft, jelly-like; supports delicate structures.

Question: What are the major cells of dense regular connective tissue? Answer: Fibroblasts.

Question: How are fibers arranged in dense regular connective tissue? Answer: Parallel collagen bundles.

Question: What is the ground substance of dense regular connective tissue like? Answer: Very little; tightly packed fibers dominate.

Question: What are the major cells of dense irregular connective tissue? Answer: Fibroblasts.

Question: How are fibers arranged in dense irregular connective tissue? Answer: Irregularly arranged thick collagen fibers; provide tensile strength in all directions.

Question: What is the ground substance of dense irregular connective tissue like? Answer: Very little; tightly packed fibers dominate.

Question: What are the major cells and fibers of elastic connective tissue? Answer: Fibroblasts, Mostly elastic fibers, some collagen.

Question: What is the ground substance of elastic connective tissue like? Answer: Sparse; allows stretch and recoil.

Question: What is the fundamental unit of collagen? Answer: All collagens are made of tropocollagen molecules.

Question: What is each tropocollagen molecule? Answer: a triple helix made of three polypeptide chains (called α-chains).

Question: Which amino acids are especially abundant in collagen? Answer: glycine, proline, and hydroxyproline.

Question: Why are glycine, proline, and hydroxyproline important in collagen? Answer: critical for the triple-helix structure.

Question: What repeating sequence is often found in collagen? Answer: Gly–X–Y, where X is often proline and Y is often hydroxyproline.

Question: What determines the collagen type? Answer: The types of α-chains (different genes code for different α-chains) and how they combine determine the collagen type.

Question: What additional factors create collagen diversity? Answer: Post-translational modifications (hydroxylation, glycosylation) and how the molecules assemble (fibrils, sheets, networks) also create diversity.

Question: Which collagen types mainly provide the skin with firmness and structure? Answer: Collagen (mainly type I & III).

Question: What happens to collagen beginning in the mid-20s? Answer: collagen production gradually declines, and the existing collagen fibers become fragmented and disorganized.

Question: How does collagen loss contribute to wrinkles? Answer: This weakening of the dermal scaffold makes the skin thinner and less resistant to folding → fine lines and wrinkles appear.

Question: What other factors contribute to wrinkle formation? Answer: elastin breakdown, proteoglycan & GAG loss, and extrinsic factors (photoaging).

Question: What causes Ehlers-Danlos Syndrome? Answer: Genetic mutations in collagen-encoding genes (e.g., COL1A1, COL3A1, COL5A1, COL5A2) or enzymes essential for collagen processing (e.g., PLOD1 which encodes lysyl hydroxylase).

Question: What connective tissue problems result from Ehlers-Danlos Syndrome? Answer: Reduced and weak collagen fibers, affecting tissue strength; Impaired collagen cross-linking, leading to weak and disorganized connective tissue; Abnormal extracellular matrix (ECM) composition.

Question: What are major skin symptoms of Ehlers-Danlos Syndrome? Answer: thin and translucent, loose, sags and wrinkles.

Question: How does Ehlers-Danlos Syndrome affect wound healing? Answer: delayed, and abnormal scarring.

Question: How does Ehlers-Danlos Syndrome affect joints? Answer: Hypermobile joints → Increased risk of dislocations and chronic joint pain due to weakened ligaments.

Question: How does Ehlers-Danlos Syndrome affect tendons? Answer: Weak tendon → Higher risk of partial or full tears.

Question: How can Ehlers-Danlos Syndrome affect bone strength? Answer: Reduced Bone Strength & Density (Osteopenia & Osteoporosis) → Higher risk of fractures.

Question: How can Ehlers-Danlos Syndrome affect bone growth? Answer: Delayed Bone Growth & Deformities → shorter bones, deformed under weight or other forces.

Question: What dental and craniofacial issues can occur in Ehlers-Danlos Syndrome? Answer: Delayed tooth eruption & misalignment; fragile teeth & increased cavities.

Question: What is the purpose of Stage 1 of wound healing? Answer: Re-establish Hemostasis: Stop bleeding by forming a clot.

Question: What occurs after vessel injury during hemostasis? Answer: blood is exposed to tissue proteins, e.g., collagens, non-blood cell surface proteins thromboplastin.

Question: What occurs during platelet aggregation? Answer: Platelets stick to the collagen fibers at the wound edges, activate clotting factors.

Question: What occurs during clotting factor activation? Answer: previously inactive clotting factors (enzymes made by the liver) are activated: including prothrombin → thrombin.

Question: How is a fibrin clot formed? Answer: Thrombin cleaves fibrinogen (a soluble protein in plasma) → fibrin monomers, which spontaneously link to form long insoluble fibrin strands.

Question: How is a fibrin clot stabilized? Answer: Factor XIIIa (activated by thrombin) crosslinks the fibrin strands.

Question: What does Factor XIIIa cross-linking produce? Answer: a strong, stable fibrin mesh that traps blood cells.

Question: What is the purpose of Stage 2 of wound healing? Answer: Inflammation: Clean up wounded tissue.

Question: What occurs to blood vessels during inflammation? Answer: Blood vessels widen and become more permeable → more blood, and immune cells enter the tissue → swelling, redness, warmth.

Question: What occurs during neutrophil infiltration? Answer: First responders neutrophils arrive, phagocytose debris/microbes, and release enzymes/ROS to disinfect the area.

Question: What happens during the monocyte-to-macrophage transition? Answer: Monocytes enter and become macrophages → continue debris clearance and release growth factors/cytokines to guide healing.

Question: What occurs during chemical signaling in inflammation? Answer: Cytokines & Growth Factors are released to recruit/activate additional immune cells and amplify the response.

Question: What is the purpose of Stage 3 of wound healing? Answer: Proliferation: Rebuild lost tissue and restore skin barrier.

Question: What do activated fibroblasts do during proliferation? Answer: Produce collagen, forming scaffold for new tissue.

Question: What occurs during angiogenesis in wound healing? Answer: New capillaries grow into the new tissue to improves oxygen/nutrient delivery.

Question: What occurs during re-epithelialization? Answer: Basal keratinocytes at wound edges migrate across the wound bed. They proliferate, migrate, and cover the wound with new epidermis.

Question: What is granulation tissue formation? Answer: Soft, pink, bumpy new connective tissue filling the wound gap.

Question: What is the purpose of Stage 4 of wound healing? Answer: Remodeling: Strengthen and mature the repaired tissue.

Question: What happens to collagen during wound remodeling? Answer: Type III collagen is replaced with stronger Type I collagen.

Question: What happens to the extracellular matrix during wound remodeling? Answer: Excess ECM is broken down; ECM is reorganized resembling normal tissue.

Question: What occurs during capillary pruning? Answer: Unneeded new blood vessels undergo apoptosis → The red, bumpy granulation tissue becomes pale and flat.

Question: What occurs during tissue contraction? Answer: Fibroblasts differentiate into myofibroblasts, which contract and pull wound edges together, reducing wound size.

Question: What happens to the final scar? Answer: May remain or fade over time depending on healing quality.

Question: What is the leading cause of mortality of burn? Answer: Sepsis is the leading cause of mortality of burn.

Question: What is the leading cause of sepsis? Answer: Infection is the leading cause of sepsis.

Question: What is sepsis? Answer: an extreme reaction to an infection, causing widespread inflammation, leading to tissue damage, organ failure, and potentially death.

Question: What is burn shock primarily caused by? Answer: hypovolemic shock due to massive fluid loss.

Question: What is shock? Answer: a life-threatening condition where the body fails to deliver enough oxygen and nutrients to tissues and organs, leading to cell damage and organ failure.

Question: What is a system? Answer: A system always involves multiple elements that are connected in specific ways.

Question: What novel property does a system display? Answer: A system always display novel properties that none of the parts possess.

Question: What is the basic equation describing a system? Answer: System = elements + specific connections between the elements.

Question: What are the levels of organization from smallest to largest? Answer: Atoms → Molecules → Cells → Tissues → Organs → Organ Systems → Organism.

Question: Where is the intelligence of biological systems embedded? Answer: the design of the elements; the connections between the elements.

Question: What are structural connections? Answer: Anatomy.

Question: What are functional connections? Answer: Physiology.

Question: What are proteins described as in the systems perspective? Answer: Nano-machines of Life.

Question: What types of enzymes are listed as protein nano-machines? Answer: anabolic; catabolic; kinase; phosphatase.

Question: What types of receptors are listed as protein nano-machines? Answer: chemical; machinal; electrical; photon; temperature.

Question: What types of channels are listed as protein nano-machines? Answer: Na+; K+; Ca2+.

Question: What types of transporters are listed as protein nano-machines? Answer: glucose; amino acids; vitamins; electron.

Question: What other protein nano-machines are listed? Answer: Motors; Highways; Adhesives; Building blocks.

Question: How can extreme pH affect proteins? Answer: Extreme pH can disrupt ionic and hydrogen bonds in a protein (not covalent bonds) leading to the loss of protein shape and function.

Question: How can temperature affect proteins? Answer: Heat, radiation, or agitation destabilize proteins.

Question: How can detergents affect proteins? Answer: Insert their hydrophobic tails into the protein’s hydrophobic core, disrupting the protein structure.

Question: How can pressure affect proteins? Answer: Hydrostatic pressure variations disrupt structure.

Question: How can solutes affect proteins? Answer: Excess salts, heavy metals etc. can damage proteins.

Question: What is the consequence of protein structure damage? Answer: Structure damage leads to loss of protein function. It is often irreversible.

Question: Why does protein structure matter? Answer: Proteins are nano-machines, their functions depend entirely on their 3-D structure.

Question: What is homeostasis? Answer: Homeostasis refers to a stable internal environment that supports the structure and function of proteins.

Question: Why is homeostasis essential for survival? Answer: The body uses all its resources to maintain this balance, which is essential for survival.

Question: What are the effectors for changing temperatures? Answer: Blood vessels; Sweat glands; Skeletal muscles; Brown fat.

Question: How do temperature receptors detect changes in temperature? Answer: Temperature changes alter ion channel structure → opening or closing.

Question: What does afferent mean? Answer: arrive at CNS.

Question: What does efferent mean? Answer: exit CNS.

Question: What are W neurons stimulated by? Answer: warm-sensitive receptors.

Question: What are W neurons inhibited by? Answer: cold-sensitive receptors.

Question: What do W neurons do to W efferent neurons? Answer: Stimulate W efferent neuron.

Question: What do W neurons do to C efferent neurons? Answer: Inhibit C efferent neuron.

Question: How do I neurons respond to temperature? Answer: insensitive to temp, auto fire at a stable frequency.

Question: What is the function of I neurons? Answer: Stabilize the thermoregulatory network by providing a steady background tone of activity.

Question: What do I neurons do to C efferent neurons? Answer: Stimulate C efferent neuron.

Question: What do I neurons do to W efferent neurons? Answer: Inhibit W efferent neuron.

Question: How do W efferent neurons integrate signals from W and I neurons? Answer: FR when W-I >0.

Question: How do C efferent neurons integrate signals from W and I neurons? Answer: FR when I-W >0.

Question: If input from W neurons is greater than input from I neurons, what happens to W efferent neuron firing? Answer: W efferent neuron firing increases.

Question: If input from I neurons is greater than input from W neurons, what happens to C efferent neuron firing? Answer: C efferent neuron firing increases.

Question: If warm-sensitive receptor activity increases, what happens to W neurons? Answer: W neuron firing increases.

Question: If cold-sensitive receptor activity increases, what happens to W neurons? Answer: W neuron firing decreases.

Question: If W neuron firing increases, what happens to W and C efferent activity? Answer: W efferent activity increases and C efferent activity decreases.

Question: If W neuron firing decreases, what happens to the influence of I neurons? Answer: The stable background activity of I neurons becomes relatively greater.

Question: If the influence of I neurons becomes greater than W neurons, which efferent pathway is favored? Answer: C efferent neurons.

Question: If W neurons are not working properly, which thermoregulatory pathway would be relatively favored? Answer: C efferent neurons because the steady activity of I neurons would dominate.

Question: If I neurons are not working properly, which thermoregulatory pathway would be relatively favored? Answer: W efferent neurons because W neuron activity would face less opposing input.

Question: In the thermoregulatory circuit, what determines whether W or C efferent neurons increase their firing? Answer: whichever input is higher, W versus I.

Question: What is the first step in the fever mechanism? Answer: Trigger- exogenous pyrogens (like LPS) activate immune cells (macrophages, dendritic cells, etc.).

Question: What is the second step in the fever mechanism? Answer: Release of Endogenous Pyrogens- activated immune cells release cytokines (IL-1β, IL-6, TNF-α, etc).

Question: What is the third step in the fever mechanism? Answer: Signal to the Hypothalamus- these cytokines circulate to the hypothalamus, stimulating the expression of COX-2.

Question: What is the fourth step in the fever mechanism? Answer: COX-2 Pathway - COX-2 converts arachidonic acid → prostaglandins, especially prostaglandin E₂ (PGE₂).

Question: What is the fifth step in the fever mechanism? Answer: PGE₂ Action on Hypothalamus- PGE₂ binds to EP3 receptors on warm-sensitive neurons in the hypothalamus, leading to reduced firing of warm-sensitive neurons.

Question: What is the physiological response when the set-point is raised? Answer: vasoconstriction, shivering, behavioral changes → fever develops.

Question: How does ibuprofen affect COX enzymes? Answer: Ibuprofen inhibits COX enzymes in CNS & periphery.

Question: How does acetaminophen affect COX enzymes? Answer: acetaminophen mainly inhibits COX enzymes in CNS.

Question: What is positive feedback? Answer: Response to a stimulus amplifies the original stimulus, moving the system further from homeostasis.

Question: What type of process commonly uses positive feedback? Answer: Usually part of a process that needs a definitive and rapid outcome, often terminated by an external event.

Question: What are examples of positive feedback? Answer: blood clotting, childbirth, lactation.

Question: What is negative feedback? Answer: Response reduces or counteracts the original stimulus, helping maintain homeostasis.

Question: What does negative feedback do to deviations from a set point? Answer: Correct deviations from a set point and restore balance.

Question: What are examples of negative feedback? Answer: thermoregulation, blood glucose regulation, blood pressure regulation, thyroid hormone regulation.