Ch 26: Urinary Ch 26: Urinary SystemSystem

Objectives

Identify and describe the components of the urinary system and their function

Describe the (histological) organization of the nephron

Identify the blood vessels that supply blood to the nephrons

Describe the blood flow through and around the nephron

Functions of Urinary System (Kidneys):

● Excretion of organic waste products

Regulation of blood

Volume

pH

Ion concentration

Kidney Kidney LocationLocation

Lateral to vertebral column in retro-peritoneal position

Surface Anatomy

Hilus

Three layers Renal fascia Adipose capsule Renal capsule

Sectional Anatomy

Cortex: light reddish brow and granular (due to many capillaries)

Medulla: darker striped appearance (due to tubules) Subdivided into distinct renal pyramids. Separated by renal columns from the cortex.

Fig 26-3

Urine collection: Ducts within each renal

papilla release urine

into minor calyx

major calyx

renal pelvis

ureter

Functional unit: Nephron

Renal corpuscle:» Glomerulus» Bowman’s capsule

Tubular passageways:» PCT» LOH» DCT» CD

(>mio/kidney)

Fig 26-4

Fig 26-5

Filtration: Passage across Three Barriers

Capillary endotheliumFenestrated

What gets through?

Basement membrane

Glomerular epithelium (= visceral layer of Bowman’s capsule)slit pores between pedicels Fig 26-5

Juxtaglomerular Apparatus

Macula densa

+Juxtaglomerular cells

(smooth muscle fibers from afferent arteriole)

= Juxtaglomerular Apparatus

= Endocrine system structure (renin and EPO)

Cortical vs Juxtamedullary Nephrons

Cortical nephrons (85%)

Juxtamedullary nephrons (15%), play keyrole in concentrating urine.

Renal Circulation

Segmental arteries

Interlobar arteries

Arcuate arteries

Interlobular arteries

Afferent arterioles

Glomerulus

Efferent arterioles

Peritubular capillaries

Segmental veins

Interlobar veins

Arcuate veins

Interlobular veins

Venules

Renal Artery

Renal Vein

Fig 26-7

Urine Transport, Storage, Urine Transport, Storage, and Eliminationand Elimination

Trace drop of urine from kidneys to outside world

Lining of these parts?

Nephroptosis (= floating kidneys)

Nephrolithiasis

Supine position Upright position: 1st degree nephroptosis:

Nephroptosis

Nephrolithiasis

occurs when urine becomes too concentrated and substances crystalize. Symptoms arise when stones begin to move down ureter causing intense pain. Kidney stones may form in the pelvis or

calyces of the kidney or in the ureter.

Anatomy of Urinary Bladder

max. holding

capacity: 1l

Detrusor muscle:• inner longitudinal• middle circular• outer longitudinal

UTIs (esp. E.coli)

Male versus Female

The End

Kidneys may sustain 90% loss of nephrons and still not show apparent symptoms!!!

2-4 % of population only have 1 kidney!

Manneken PisFountain

Brussels, 1619