Nonspecific and Specific Defense System Happening at the Same Time

Immune System:

·  Nonspecific and specific defense system happening at the same time

·  Nonspecific defense is faster

·  First line of defense: skin and mucous membranes: lower pH of skin hurts pathogens but not us cause tough skin cells, tears have enzymes that will kill bacteria, mucus catches bacteria in nose, cilia sweep dust and bacteria-laden mucus from lower respiratory passages, lipids in sweat, HCl and protein-digesting enzymes of the stomach

·  Second line: Antimicrobial proteins, phagocytes, and other cells inhibit invaders, inflammation is good, nonspecific, Natural killer cells (blow up bad things instead of “eat” them), fever

·  1. Adherence of phagocyte to pathogen- facilitated by opsonization (coating of pathogen by complement proteins or antibiotics to make it sticky)

·  Phagocytosis

o  Phagocyte adheres to pathogens or debris

o  Phagocyte forms pseudopods that eventually engulf the particles forming a phagosome

o  Lysosome fuses with the phagocyte vesicle, forming a phagolysosome

o  Lysosomal enzymes digest the particles, leaving a residual body

o  Exocytosis of the vesicle removes indigestible and residual material

·  Phagocyte Mobilization (get phagocyte to infected area):

o  1. Leukocytosis: release of neutrophils from bone marrow in response to leukocytosis-inducing factors from injured cells

o  2. Margination: neutrophils cling to the walls of capillaries in the inflamed area

o  3. Diapedesis of neutrophils (squeeze through capillary wall)

o  4. Chemotaxis: inflammatory chemicals (chemotactic agents) promote positive chemotaxis of neutrophils (drawing neutrophils to the site of infection)

Renal System:

·  Kidneys are major excretory organs

·  Urinary bladder is temporary storage reservoir for urine

·  Ureters transport urine from the kidneys to the bladder

·  Urethra transports urine out of body

·  Kidneys are highly vascularized because function in removal of toxins, metabolic wastes, and excess ions from the blood, and regulation of blood volume, chemical composition, and pH

·  Other functions:

o  Gluconeogenesis during prolonged fasting

o  Renin: regulation of blood pressure and kidney function

o  Erythropoietin: regulation of RBC production

o  Activation of vitamin D (metabolism)

·  Three layers of tissue

o  Renal fascia: anchoring outer layer of dense, fibrous connective tissue that anchors the kidney in place

o  Perirenal fat capsule: fatty cushion that cushions the kidneys

o  Fibrous capsule: prevents spread of infection to kidney

·  Renal arteries deliver about ¼ of cardiac output to the kidneys each minute

·  Arterial flow into (oxygenated) and venous flow out of (deoxygenated) of the kidney follow similar paths

·  Nerve supply is via sympathetic fibers from the renal plexus

·  1. Afferent arteriole delivers blood to the glomerulus, efferent arterioles carry blood away from the glomerulus (not as much fluid?)

·  Blood pressure is high because efferent arterioles are smaller in diameter than afferent arterioles (smaller diameter=more pressure)

·  Efferent feed into one of two places:

·  2. Peritubular capillaries: low pressure, porous capillaries adapted for absorption (absorb solutes and water), arise from efferent arterioles, cling to adjacent renal tubules in cortex, empty into venules

·  3. Vasa recta: long vessels parallel to long loops of Henle, arise from efferent arterioles of juxtamedullary nephrons, function in forming in concentrated urine

·  SO many nephrons, all work at same time, 2 parts:

o  Glomerulus: a tuft of capillaries that filter the blood

o  Renal tubule: begins as cup-shaped glomerular (Bowman’s) capsule surrounding the glomerulus (baseball mitt-holds glomerulus)

·  Renal corpuscle: glomerulus + capsule

·  Glomerulus: fenestrated, glomerular endothelium allows filtrate to pass from plasma into the glomerular capsule

o  Parietal layer: simple squamous epithelium, just provides support

o  Visceral layer: branching epithelial podocytes- foot processes cling to basement membrane, has filtration slits that allow filtrate to pass into the capsular space

·  Proximal Convoluted Tubule:

o  Cuboidal cells with dense microvilli and large mitochondria, functions in reabsorption and secretion, confined to cortex

·  Loop of Henle:

o  Thin segment made of simple squamous epithelium that is freely permeable to water is in the descending limb

o  Thick segment is ascending limb, cuboidal to columnar cells where water cannot get out of

·  Distal convoluted Tubule:

o  Cuboidal cells with few microvilli, function more in secretion than reabsorption

·  Collecting ducts: receive filtrate from many nephrons, fuse together to deliver urine through papillae into minor calyces

o  Intercalated cells: cuboidal cells with microvilli, maintain acid-base balance in body

o  Principal cells: cuboidal cells without microvilli, maintain body’s water and salt balance

·  Cortical Nephrons: 85% of nephrons, almost entirely in cortex

·  Juxtameduallary nephrons- long loops of Henle deeply invade the medulla, important in the production of concentration urine

Urine Formation

·  1. Glomerular filtration

·  2. Tubular reabsorption: returns all glucose and amino acids, 99% of water, salt, and other components to the blood

·  3. Tubular secretion: reverse of reabsorption, selective addition to urine

Filtration Membrane: porous membrane between the blood and capsular space

·  1. Fenestrated endothelium of the glomerular capillaries

·  2. Visceral membrane of GC, podocytes, foot-like processes, filtrate slits

·  3. Gel-like basement membrane (fused basal laminae of the other two layers)

·  Allows passage of water and solutes smaller than most plasma proteins

o  Fenestrations prevent filtration of blood cells (no blood in urine)

o  Negatively charged basement membrane repels large anions such as plasma proteins

o  Slit diaphragms also help to repel macromolecules if they slip through the slits

·  Glomerular mesangial cells: engulf and degrade macromolecules caught up in filtration membrane, can contract to change the total surface are available for filtration

Step 1: Glomerular Filtration

·  Passive, mechanical process driven by hydrostatic pressure, highly efficient

o  FM permeable, large surface area, glomerular pressure high

·  Large molecules are not filtered, protein or blood in urine indicate problem with the filtration membrane

·  Glomerular filtration rate: volume of filtrate formed per minute by both kidneys (120-125 ml/min)

o  Depends on: total surface area available for filtration, FM permeability, Net flitration pressure

·  Controls:

o  Intrinsic (renal autoregulation)- act locally within the kidney

o  Extrinsic controls- nervous and endocrine mechanisms that maintain blood pressure, but affect kidney function

·  Intrinsic:

o  Maintain a nearly constant GFR when MAP (mean arterial pressure) is in the range of 80-180 mm Hg

o  Two types: myogenic mechanism, tubuloglomerular feedback mechanism, which senses changes in the juxtaglomerular apparatus