Urinary system

urinary systemKarla Mae J. Sagun, OTRP

OUTLINEOUTLINE• Functions of the Urinary System• ANATOMY– Different Structures of the Urinary System– The KIDNEY– Blood Vessels– The NEPHRON• PHYSIOLOGY• Urine Formation• Urine Movement• Regulation of Urine Concentration and Volume• Regulation of Extracellular Fluid Composition• Regulation of Acid-Base Balance

FUNCTIONS

1. Excretion 2. Regulation of blood volume and pressure3. Regulation of the concentration of solutes

in the blood4. Regulation of extracellular fluid pH5. Regulation of red blood cell synthesis6. Vitamin D synthesis

STRUCTURES OF THE URINARY SYSTEM

KidneysUretersUrinary BladderUrethra

The KIDNEY

• bean-shaped organ• size of a tightly clenched fist• lie on the posterior abdominal wall

(RETROPERITONEAL)• T12 – L3

Structures of the Kidney

• Renal capsule:– surrounds, encloses, and protects the kidney. – helps to maintain the shape of the kidney as well as protecting it from

damage. – The renal capsule is itself surrounded by a mass of fatty tissue that also

helps to protect the kidney by damage by cushioning it in cases of impact or sudden movement.

• Renal hilus:– indentation near to the centre of the concave area of the kidney. – the area of the kidney through which the ureter leaves the kidney and the

other structures including blood vessels (illustrated), lymphatic vessels, and nerves enter/leave the kidney.

• Renal cortex:– outer part of the kidney and has a reddish colour (shown as very pale

brown above). – is the location of the Bowman's Capsules and the glomeruli, in addition to

the proximal and distal convoluted tubules and their associated blood supplies

• Renal medulla:– inner part of the kidney.

• Renal pyramids:– There are approx. 5 - 18 striated triangular structures called "Renal

Pyramids" within the renal medulla of each kidney. The appearance of striations is due to many straight tubules and blood vessels within the renal pyramids.

– RENAL PAPILLA: point of a pyramid

• Renal columns:– Cortical tissue that dips into the medulla between the pyramids.

• Calyx:– Considered the beginning of the plumbing system of the urinary

system– Collects urine leaving from the papilla (throught the papillary

duct) for transport out of the body

Renal pelvis:– The renal pelvis is the funnel-shaped basin (cavity) that receives

the urine drained from the kidney nephrons via the collecting ducts and then the (larger) papillary ducts.

CROSS SECTION OF A KIDNEY

Diagram showing the parts of the KIDNEY and the NEPHRON

Blood Vessels of the KidneyAbdominal aorta

Renal arterySegmental arteries

Lobar arteriesInterlobar arteries

Arcuate arteriesInterlobular arteries

Inferior vena cavaRenal vein

Segmental veinsLobar veins

Interlobar veinsArcuate veins

Interlobular veins

Afferent arterioleGlomerulus (GLOMERULAR CAPILLARIES)

Efferent arteriolePeritubular arteries –vasa recta

The NEPHRON

• Functional unit of the kidney• 1.25 M per kidney• Make up the bulk of the kidney

• CORTICAL NEPHRON• JUXTAMEDULLARY NEPHRON

MICROSCOPIC STRUCTURES OF THE NEPHRON

Renal corpuscle*Bowman’s capsule

Proximal convoluted tubule*Loop of HenleDistal convoluted tubule*Collecting duct

NEPHRON

RENAL CORPUSCLE

• BOWMAN’S CAPSULE– Cup-shaped mouth of the nephron– Consists of 2 layers of epithelial cells with Bowman’s space

between them– Inner layer lined with podocytes + glomerular capillaries

FILTRATION MEMBRANE– GLOMERULAR FILTRATE – – PEDICELS – FILTRATION SLITS – SLIT DIAPHRAGM

• GLOMERULUS– Structure fitted into Bowman’s capsule– It is a network of fine capillaries– Have thin, membranous walls that are composed of a single

layer of endothelial cells

RENAL TUBULES

URETER

• Begins at L1• 28-34 cm long• Propels urine by peristalsis

3 layers of tissue:1.Mucous lining2.Muscular layer3.Fibrous outer layer

URINARY BLADDER2 Major Functions:1. Reservoir for urine2. Expels urine through the

urethra

muscular collapsible bag located behind the symphysis pubis and in front of the rectum

DETRUSOR MUSCLE – smooth muscle tissue which makes up the wall of the bladder

TRIGONE -

URETHRA

• Leads from the floor of the urethra to the exterior of the body

• FEMALE• 3 cm• Urinary

• MALE• 20 cm• Genito-urinary

FEMALE URETHRA

MALE URETHRA

URINE PRODUCTION

1. Filtration Glomerular-capsular membrane

2. Reabsorption Renal tubule

3. Secretion

FILTRATION• Physical process• Movement of water and protein-free solutes

from the plasma in the glomerulus• 180L of glomerular filtrate formed each day

• FILTRATION PRESSURE – pressure gradient that forces fluid from the glomerular capillary filtration membrane Bowman’s capsule

1. BP in the glomerular capillaries2. Blood protein concentration3. Pressure in the Bowman’s capsules

REABSORPTION

• Second step which takes place by means of passive and active transport mechanisms from all parts of the renal tubules

• Movement of molecules out of the various segments of the tubule and into the peritubular blood

PROXIMAL TUBULE

• Cuboidal cells with numerous microvilli and mitochondria

Primary site for the reabsorption of solutes and water

65% of filtrate volume reabsorbed

Summary of Reabsorption:1. Sodium by active transport2. Glucose and amino acids by cotransport3. Chloride by passive transport ( due to electrical imbalance)4. Water by osmosis5. About half of urea by passive transport

LOOP OF HENLE• Functions to further concentrate the filtrate

• DESCENDING LIMB– Water moves out of the nephron by osmosis– Some solutes move into the nephron by diffusion– 15% of filtrate reabsorbed

• ASCENDING LIMB– Functions to dilute the filtrate by removing solutes

(sodium, potassium, chloride by active transport)

DISTAL TUBULE and COLLECTING DUCTS

Functions to remove water and additional solutes Reabsorption of water in these segments are

controlled by hormones ANTIDIURETIC (ADH) HORMONE

DISTAL TUBULE Reabsorb sodium by active transport Reabsorb water by osmosis Secretion of potassium and hydrogen ions

COLLECTING DUCTS Reabsorption of water by osmosis

TUBULAR SECRETION

• Movement of molecules out of the peritubular blood and into the tubule for excretion

URINE MOVEMENT

• MICTURITION REFLEX•Mechanism for voiding urine

• Voluntary relaxation of external sphincter muscle of the bladder

CHARACTERISTICS OF URINENORMAL ABNORMAL

Color Transparent yellow, amber or straw color

Cloudiness

Compounds Mineral ionsNitrogenous wasteSuspended solidsUrine pigments

AcetoneAlbuminBileGlucose

Odor Slight odor Acetone odor

pH 4.6 – 8.0

Specific Gravity 1.001 – 1.035 High specific gravity: high precipitation of solutes

URINE COMPOSITION

• 95% water• Dissolved substances:

1. Nitrogenous wastes2. Electrolytes3. Toxins4. Pigments5. Hormones6. Other abnormal constituents

HOW THE KIDNEYS PERFORM THEIR FUNCTIONS

REGULATION OF URINE CONCENTRATION AND VOLUME

• Hormonal Mechanisms– Antidiuretic Hormone

• Secreted by posterior pituitary gland• Regulates amount of H2O reabsorbed by the distal tubules and

collecting ducts• ADH : H2O reabsorbed

– Renin – Angiotensin – () Aldosterone • Conserve water to help prevent further decline in BP• ALDOSTERONE : reabsorption of Na + and Cl –

– Atrial natriuretic hormone• Secreted from cardiac muscle cells in the RA when there is a in

BP• ANH : reabsorption : urine output : blood volume and BP

• Sympathetic vs. Parasympathetic Innervation

– sympathetic activity: blood flow : filtrate formation : urine formation

REGULATION OF EXTRACELLULAR FLUID COMPOSITION

• HOMEOSTASIS• Body Fluids– ECF (40%) vs. ICF (60%)

Thirst Sensation of thirst increases if ECF becomes more

concentrated or if BP decreases

Ions Sodium ions Potassium ions Calcium Phosphate and Sulphate ions

REGULATION OF ACID-BASE BALANCE

• Concentration of H+ : pH of body fluids• Normal pH: 7.35 – 7.45• Acidosis: below normal pH• Alkalosis: above normal pH

• Controlled by:1. Buffers

• Chemicals that resist change in pH of a solution

2. Respiratory system• Increased RR raises pH rate of CO2 elimination is increased

3. Kidneys• Excrete H+ in response to decreased blood pH

ACIDOSIS and ALKALOSIS

• RESPIRATORY ACIDOSIS– When respiratory system is unable to eliminate

adequate amounts of CO2• METABOLIC ACIDOSIS– Excess production of acidic substances

• RESPIRATORY ALKALOSIS– hyperventilation

• METABOLIC ALKALOSIS– Rapid elimination of hydrogen ions such as in

vomiting or when excess aldosterone is excreted

kms, otrp