AP II exam 3 short answer

What is the sequence of vessels through which lymph flows in its route back to the blood? What are the two collecting ducts, and what parts of the body do they drain?

• Lymphatic capillaries → collecting vessels → 6 lymphatic trunks → 2 collecting ducts →subclavian veins

• Right lymphatic duct: empties into right subclavian vein

• Thoracic duct: empties into left subclavian vein

List and describe the four main mechanisms by which the complement system mediates an immune response.

• inflammation

  • C3a stimulates mast cells & basophils to secrete histamine & other inflammatory chemicals

  • Activates & attracts neutrophils and macrophages

• immune clearance

  • C3b binds antigen–antibody complexes to RBC’S

  • RBCs circulate through liver & spleen; macrophages strip off & destroy Ag–Ab complexes RBCs unharmed

• phagocytosis

  • C3b assists by OPSONIZATION

  • Coats microbial cells with opsonins - serve as binding sites for phagocyte attachment

• cytolysis

  • C3b splits complement protein C5 into C5a & C5b

  • C5b binds to enemy cell, attracts more complement proteins, & forms a membrane attack complex

    • Forms a hole in the target cell

    • Electrolytes leak out, water flows in rapidly, cell ruptures

Choose two of the lymphatic organs discussed in class and describe their anatomy (in detail) and function.

tonsils:

• Patches of lymphatic tissue located at the entrance to the pharynx

  • Guard against ingested or inhaled pathogens

  • Covered with epithelium

  • Have deep pits: tonsillar crypts lined with lymphatic nodules

• Three main sets of tonsils:

  • Palatine tonsils

  • Lingual tonsils

  • Pharyngeal tonsil (adenoids)

Spleen:

• Parenchyma exhibits two types of tissue

  • Red pulp: sinuses filled with erythrocytes

  • White pulp: lymphocytes, macrophages surrounding small branches of splenic artery

• Functions include:

  • For old, fragile RBCs, spleen is “erythrocyte graveyard”

  • Blood cell production in fetus (and very anemic adults)

  • White pulp monitors blood for foreign antigens and keeps an army of monocytes for release when needed

  • Stabilizes blood volume through plasma transfers to lymphatic system

• Spleen is highly vascular and vulnerable to trauma and infection

Describe the sequence of events at the immune level that occur during inflammation from an injury..

• Monocytes arrive & become macrophages

  • Engulf & destroy bacteria, damaged host cells, and dead & dying neutrophils; act as antigen presenting cells

• Edema – swelling compresses veins, reduces venous drainage, forces open lymphatic valves, promoting lymphatic drainage

  • Lymphatic vessels collect & remove bacteria, dead cells, tissue debris

• Platelet-derived growth factor is secreted by blood platelets and endothelial cells in injured area

  • Stimulates fibroblasts to multiply & synthesizes collagen

• Hyperemia delivers oxygen, amino acids, and other necessities for protein synthesis

  • Increased heat increases metabolic rate, speeds mitosis and tissue repair

• Fibrin clot forms a scaffold for tissue reconstruction

• Pain makes us limit the use of a body part so it has a chance to rest and heal

List and describe the four ways of acquiring antibodies discussed in lecture, and give an example of each.

• Natural active immunity (recovering from flu)

  • Production of one’s own antibodies or T cells as a result of natural exposure to an antigen

• Natural passive immunity (breast milk, antibodies passed from mother to baby)

  • Temporary immunity that results from antibodies produced by another person

• Artificial active immunity (flu shot)

  • Production of one’s own antibodies or T cells as a result of vaccination against disease

• Artificial passive immunity (rabies immunoglobulin)

  • Temporary immunity that results from the injection of immune serum (antibodies) from another person or animal

Describe the pathway through which air travels on its way from our nose (or mouth) to our alveoli. What occurs at each of these structures?

Nose (filters, warms) -> pharynx (assists in swallowing and speech) -> larynx (voice) -> trachea (rigid air tube)-> bronchi (Directs the airflow to the right and left) -> lungs → Incoming air stops in the alveoli (gas exchange occurs here)

How does our autonomic control system regulate our breathing rates? What are the major areas of the brain responsible for the respiratory cycle, how do they interact with each other, and what does each do?

• Automatic breathing is controlled by respiratory centers in the medulla oblongata and pons.

• The ventral respiratory group (VRG) in the medulla generates the basic breathing rhythm (2 sec inhale, 3 sec exhale in quiet breathing).

• The dorsal respiratory group (DRG) modifies breathing rate and depth based on sensory input.

• The pontine respiratory group (PRG) in the pons fine-tunes the rhythm and adjusts breathing for activities like exercise, sleep, and speech.

• VRG = rhythm

• DRG = depth

• PRG = pattern adjustment

What is the major driver of ventilation (air flow through the lungs)? What is the sequence of events that occurs during the respiratory cycle in terms of how air moves in and out of the lungs, and what are the major muscles involved?

• major driver is co2 levels

• Diaphragm

  • Prime mover of respiration

  • Contraction flattens diaphragm,

  enlarges thoracic cavity and pulls air

  into lungs

  • Relaxation allows diaphragm to

  bulge upward, compresses lungs

  and expels air

• Internal and external intercostal

  muscles

  • Synergists to diaphragm; located

  between ribs

  • Stiffen the thoracic cage during

  respiration and prevent it from

  caving inward when diaphragm

  descends

  • Contribute to enlargement and

  contraction of thoracic cage

Why is pressure so important in the respiratory system? Discuss the relative partial pressures of oxygen and carbon dioxide at different points in our circulatory pathway. Where is the PO₂ higher, and why? Where is the PCO₂ higher, and why?

• air moves from high to low pressure

• Gases move from high → low pressure

• Oxygen (O₂):

  • Higher in lungs → moves into blood

  • Lower in tissues → diffuses into cells

• Carbon dioxide (CO₂):

  • Higher in tissues → enters blood

  • Higher in blood → moves into lungs

• The greater the PO2 in the alveolar air, the

more O2 the blood picks up

• Since blood arriving at an alveolus has a higher

PCO2 than air, it releases CO2 into the air

How is the carbon dioxide level in the blood related to the blood pH? Discuss the physiological responses of the respiratory system to both acidosis and alkalosis.

• CO₂ + H₂O → carbonic acid → lowers pH

• Acidosis (low pH):

  • Hyperventilation can be a corrective homeostatic response to acidosis

• Alkalosis (high pH):

  • Hypoventilation can be a corrective homeostatic response to alkalosis

What is the countercurrent multiplier? What is its main function, and how does it work? Reference the anatomy and the flow of fluid and solute.

• Function: creates concentration gradient in medulla → allows water reabsorption

• How it works:

  • Descending limb: permeable to water → water leaves

  • Ascending limb: pumps out Na⁺/Cl⁻ → not permeable to water

  • Loop creates osmotic gradient → concentrates urine

Discuss the forces involved in glomerular filtration. Which force needs to override the other to filter the blood, and why? How does this relate to the anatomy of the blood vessels entering and exiting the glomerulus?

• Forces:

  • Glomerular hydrostatic pressure (pushes fluid out)

  • Blood colloid osmotic pressure (pulls fluid in)

  • Capsular pressure (resists filtration)

• Filtration occurs when:

  • Hydrostatic pressure > opposing forces

• Anatomy connection:

  • Afferent arteriole larger than efferent → increases pressure

What is the Renin-Angiotensin-Aldosterone mechanism? How does it work and why is it important?

• Renin is secreted by granular cells when BP drops dramatically

• Renin converts angiotensinogen into angiotensin I

• In lungs & kidneys, angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II

  • Works to restore fluid volume & BP

• Angiotensin II — active hormone that increases BP

  • Constricts efferent arterioles to raise GFR

  • Lowers BP in peritubular capillaries enhancing reabsorption of NaCl and H2O • Stimulates adrenal cortex to secrete aldosterone -> Na+ and H2O reabsorption in DCT & collecting duct

  • Stimulates Na+ and H2O reabsorption in PCT

  • Stimulates posterior pituitary to secrete ADH Stimulates thirst and H2O uptake

• Trigger: low blood pressure or low sodium

• Steps:

  • Kidney releases renin

  • Renin → angiotensin I → angiotensin II

  • Angiotensin II:

    • Vasoconstriction

    • Releases aldosterone → Na⁺ and water reabsorption

• Result: increases blood pressure

Describe the two routes of reabsorption that occur in the tubules of the kidneys. Which solutes pass between each route and why?

• Transcellular (through cells):

  • Glucose, amino acids, ions → need transporters

• Paracellular (between cells):

  • Water and some ions → move via diffusion

Describe the process of micturition, how it is stimulated, and the anatomical structures involved. What differs physiologically between an infant and a child/adult who is potty trained?

• Process:

  • Bladder fills → stretch receptors activated

  • Signals spinal cord

  • Detrusor muscle contracts

  • Internal sphincter relaxes (involuntary)

  • External sphincter relaxes (voluntary)

• Infant vs adult:

  • Infants: reflex only (no control)

  • Adults: brain control over external sphincter

How do the concentrations of the major electrolytes differ in intracellular vs. extracellular compartments? How does this relate to the resting membrane potential?

• Intracellular fluid (ICF) Volume = 25 L 65% of fluid

• Extracellular fluid (ECF) Volume = 15 L 35% of fluid. Interstitial fluid (IF) Volume = 12 L 25% of fluid (Plus ~2% transcellular fluid)

• Intracellular fluid (ICF): high K⁺

• Extracellular fluid (ECF): high Na⁺

• Relation to resting membrane potential:

  • K⁺ leaving cell → negative charge inside

  • Creates resting membrane potentia

What are the two ways we inhibit the sensation of thirst? Describe the stimulus, mechanism, and result of each

• Short-term inhibition of thirst:

  • Cooling and moistening of mouth quenches thirst

  • Distension of stomach and small intestine

  • 30 to 45 minutes of satisfaction

    • Must be followed by water being absorbed into the bloodstream or thirst returns

  • Helps to prevent overdrinking

• Long-term inhibition of thirst:

  • Absorption of water from small intestine reduces osmolarity of blood

  • Stops the osmoreceptor response, promotes capillary filtration, and makes saliva more abundant and watery

  • 30 minutes or longer to take effect

What is the main function of antidiuretic hormone? Discuss the different triggers that will cause you to secrete it and explain the different consequences of its secretion

produced by hypothalamus to promote water conservation

• Triggers:

  • triggered by hypothalamic osmoreceptors in response to dehydration

  • High blood osmolarity

  • Low blood volume

• Effects:

  • Kidneys reabsorb more water

  • Urine becomes concentrated

  • Blood volume increases

ADH system is example of negative feedback

If osmolarity rises and/or blood volume falls, more ADH is secreted

If osmolarity falls and/or blood volume rises, ADH release is inhibited, so tubules reabsorb less water, urine output increases

What is a buffer system? Describe how the bicarbonate buffer system works.

• Buffer: any mechanism that resists changes in pH

  • Convert strong acids or bases to weak ones

• Solution of carbonic acid and bicarbonate ions that participate in a reversible reaction:

• CO2 + H2O ←→ H2CO3 ←→ HCO3 − + H+

• The direction of the reaction determines whether it raises or lowers pH • Lowers pH by releasing H+ (more acidic)

• Raises pH by binding H+ (more basic)

• The bicarbonate buffer system coordinates with the lungs and kidneys to help control pH and CO2

• To lower pH, kidneys excrete HCO3 − • To raise pH, kidneys excrete H+ and lungs excrete CO2