The Urinary System

Functions of the Urinary System Removal of metabolic wastes (especially nitrogenous wastes e.g. urea & uric acid). Water balance (and therefore blood pressure). Control of electrolyte balance. Control of pH. Removal of toxins.

Anatomy of the Urinary System The Kidneys: the functional heart of the urinary system. The Ureters: pipeline from the kidneys to the bladder. The Urinary Bladder: holding tank of urine. The Urethra: avenue of relief (word of the day “micturition” = voiding the bladder)

Urinary System Components

The Kidneys Location: retroperitoneal against the dorsal wall of the abdominal cavity. The right kidney is slightly lower than the left. Size & weight: approximately 150 grams (about 5 ounces) each and 12 cm x 10 cm x 4 cm. Shaped like a bean (or are beans shaped like kidneys?)

The Position of the Kidneys Figure 26–2

Gross Anatomy of the Urinary System Figure 26–3

The Structure of the Kidney Figure 26–4

Blood Supply to Kidneys Kidneys receive 20–25% of total cardiac output 1200 - 1500 ml of blood flows through kidneys each minute Kidney receives blood through renal artery

Blood Supply to the Kidneys Figure 26–5

A slice of kidney Cortex Medulla Glomeruli Capsule

The Nephron: functional unit of the kidney Interlobular artery Afferent Arteriole Glomeruli

Functional Anatomy of Nephron and Collecting System Figure 26–6

Renal Corpuscle

Filtrate & Urine flow

Cortical and Juxtamedullary Nephrons Figure 26–7

The renal corpuscle and the Juxtaglomerular apparatus

The renal filtration membrane: Podocytes and fenestrated capillaries

Filtration slits Pedicles

The filtration membrane

An Overview of Urine Formation Figure 26–9 (Navigator)

Filtration pressures: NFP must be positive for U2P

Formation of dilute urine

After the Kidneys: the bladder & urethra

Male Figure 26–18a

Female v Figure 26–18c

It can hold a maximum of 800 – 1000 ml!

Histology

Composition of Urine Abnormal Normal Glucose “glycosuria” Urea Proteins “proteinuria” or “albuminuria” Ketones “ketonuria” Hemoglobin “hemoglobinuria” Erythrocytes “hematuria” Bile pigments “bilirubinura” Leukocytes “pyruia” Normal Urea Uric acid Creatinine Na K Phosphates Sulfates Bicarbonate Ca Mg Abnormally low output = oliguria No output = anuria Abnormally high output = polyuria Diuresis = increased urine output Diuretic = substance that leads to diuresis

Kidney stones

“Well Mr. Osborne, I don’t think that it’s kidney stone after all”