Note Taking Guide Chapter 20:The Urinary System

Organs :

Function:
        Waste management

        Regulate blood volume and composition

        Regulate blood pH

        Regulate blood pressure

        Contribute to metabolism:
                    calcitriol
                   
                    erythropoietin

                    gluconeogenesis

Location:

Surrounded by:

Anatomy
            Renal hilum

            Renal sinus

            Renal cortex

            Renal medulla:
                       renal pyramids

                        renal papilla

            Renal columns

            Papillary ducts

            Minor calyces

            Major calyces

            Renal pelvis

            Ureter

The Functional unit: The nephron

Functions:

Structure:
        Renal corpuscle:
                    Glomerulus

                    Bowman’s capsule

    Renal tubules:
                proximal convoluted tubule

                nephron loop (Loop of Henle)

                distal convoluted tubule

                collecting duct

Cortical nephrons

Juxtamedullary nephrons

Blood Supply:
            Renal artery

                        afferent arteriole

                                capillary network called the glomerulus

efferent arteriole

                            vasa recta

                            second capillary network - the peritubular capillaries

            Renal vein

Nerve Supply:
    Sympathetic innervation - control diameter of arterioles, regulating blood flow

The Renal Corpuscle:
            function:

            Structure:
                    Bowman’s capsule
                            outer layer - simple squamous epithelium

                           inner layer - podocytes

                                        plus endothelium of capillaries = filtration membrane

                                        fenestrated endothelium of glomerulus - stops cells

                                        basement membrane of glomerulus - stops large proteins

                                        slit membrane - stops medium sized proteins

Filtration:
            180 Liters/ day filtered, all but 1-2 L is reabsorbed

                    capillaries are porous and thin

                    capillaries are long - high surface area

                    capillary blood pressure is high

Forces opposing filtration:
            capsular hydrostatic pressure

            capillary osmotic pressure

Net filtration pressure:
            Glomerular filtration rate (GFR)

            Glomerular blood flow depends on:
                            renal autoregulation
                                    juxtaglomerular apparatus (JGA)

                                    regulates blood pressure and filtration rate

                                    hormonal regulation:
                                            renin - angiotensin -II , a potent vasoconstrictor

                                    neural regulation

Tubular Reabsorption:
                Proximal convoluted tubules

                        cells cuboidal and have microvilli

                        peritubular capillaries

                        transport maximum

                        renal threshold

                                    diuresis

                                    diabetes mellitus

        Distal convoluted tubule and collecting ducts:
                principal cells
                        Aldosterone

                        ADH

                intercalated cells

Tubular Secretion:
            substances actively transported out of the plasma into the urine

            Funtions:
                    1. secretion of substances eliminate them from the body

                    2. secretion of H⁺ helps maintain blood pH

Production of dilute and concentrated urine:
            Mechanism of urine dilution:
                In the abscence of Antidiuretic hormone (ADH) the distal convoluted tubules and collecting ducts are impermeable to water.

                    Aldosterone may cause sodium reabsorption

                    Water cannot be reabsorbed.

        Mechanism of urine concentration:
                    Countercurrent mechanism in the loop of Henle

                    Establishes a concentration gradient within the medulla of the kidney.

                When ADH is present, water is reabsorbed and urine is concentrated.

                            After urine leaves the collecting ducts its composition and concentration is NOT changed by the passage through the rest of the urinary system.

                        Diuretics - cause increased urine output.
                            Lasix - prevents Na transport in ascending limb of nephron loop

                    Dialysis

Ureters:
            connect kidneys to bladder

            retroperitoneal

        Layers:
                    mucous coat or mucosa

                            transitional epithelium

                            secretes mucus

                            muscluar coat or muscularis

                            fibrous coat

                            blood &lymphatic vessels, & sensory nerves

Urinary bladder:

            Location

            Function

            Anatomy:

                        trigone

            Histology:
                    mucous coat or mucosa

                    transitional epithelium

                    rugae

                    submucous coat

                    muscular coat - detrusor muscle

                    serous coat

Micturition - urination

Urethra:
        mucous membrane

        muscular layer - longitudinal smooth muscle fibers

        In females - only 4 cm long

                        ends at external urethral orifice or urinary meatus

        In males -

                    prostatic urethra

                    membranous urethra

                    penile or spongy urethra