BIO120 Mod 11 PPT (Urinary System 2024)

Urinary System Overview

The urinary system plays a crucial role in the human body by performing vital functions related to waste removal, maintaining homeostasis, and regulating various bodily fluids.

Functions of the Urinary System


  1. Excretion of Metabolic Wastes primary waste: urea, a nitrogenous compound, which is formed in the liver from ammonia and carbon dioxide.

    Other wastes: ammonium, uric acid, and creatinine.


  2. Maintain Blood Acid-Base BalanceThe kidneys monitor blood pH (normal range 7.35-7.45) by excreting hydrogen ions and reabsorbing bicarbonate.


  3. Maintain Water-Salt BalanceThe kidneys regulate blood pressure through fluid and ion balance by adjusting the reabsorption of water (via osmosis) and various ions in response to the body’s needs, ultimately impacting overall blood volume.


  4. Secretion of HormonesThe kidneys secrete erythropoietin, which stimulates erythrocyte (red blood cell) production in the bone marrow when blood oxygen levels are low.

Organs of the Urinary System


  • Kidneys:Responsible for filtering waste from the blood,


  • Ureters:Two elongated tubes that transport urine from the kidneys to the bladder through peristaltic movements using smooth muscle contractions.


  • Urinary Bladder:A muscular sac that stores urine


  • Urethra:A tube through which urine exits the body

Sphincter Muscles in the Bladder

There are two sphincter muscles at the bladder opening:

  • Internal Sphincter: Composed of smooth muscle, this sphincter is under involuntary control, allowing urine to flow into the urethra when the bladder is full.


  • External Sphincter:Made of skeletal muscle, this sphincter is voluntarily controlled, enabling conscious control over urination.

Kidney Anatomy

Location:

The kidneys are situated near the lower back, lateral to the vertebral column; the right kidney is typically lower than the left due to the large liver's size and position.

External Structure of the Kidney


  • Renal Capsule:A tough, fibrous tissue covering that provides protection to the kidney.


  • Renal Hilum:The concave side where renal blood vessels, ureters, and nerves enter or exit the kidney.

Internal Structure of the Kidney


  • Renal Cortex:The outermost layer


  • Renal Medulla:The middle region characterized by renal pyramids

    Renal Pelvis:The innermost area where urine collects before moving into the ureters.

Figures and Diagrams

Kidney Structure Diagram:

Identifying key components such as:

  • Renal Cortex

  • Renal Medulla

  • Hilum

  • Renal Pelvis

  • Fibrous Capsule

Blood Supply to the Kidney


  • Renal Artery:Branches off from the abdominal aorta

    Renal Vein: connects to the inferior vena cava to return filtered blood to the heart

    • Structures to Know in the Kidney

  • Cortical Blood Vessels

  • Arcuate and Interlobar Blood Vessels

  • Minor and Major Calyx

  • Renal Pelvis

  • Renal Hilum

  • Renal Pyramid

  • Papilla

The Nephron

Each kidney houses approximately 1 million nephrons, which are the functional units of the urinary system responsible for urine formation.

Parts of the Nephron


  • Glomerular Capsule:Closed cuplike end that surrounds the glomerulus


  • Proximal Convoluted Tubule:Twisted part of tube, closest to capsule


  • Nephron Loop (Loop of Henle):Descending tube that makes a U-turn


  • Distal Convoluted Tubule: Twisted part of tube further from glomerular capsule


  • Collecting Duct: collects urine and drains into renal pelvis.

Blood Flow Through the Nephron

The renal artery branches off the abdominal aorta to supply the kidneys. The smaller afferent arteriole enters the glomerular capsule and becomes a knot of capillaries called the glomerulus. Blood leaves through the efferent arteriole and branches into a peritubular capillary network, which surrounds the nephron. Filtered blood returns to the heart through the renal vein which leads to the inferior vena cava

Steps of Urine Formation


Glomerular Filtration:Blood is filtered in the glomerulus

  • Filter done by size

  • Remains in large capillary (elements:plasma proteins)

  • Filtered out (small)
    water

    nitrogenous waste

    nutrients

    ions (salts)

Tubular Reabsorption:tubule to blood

Important nutrients, water & some urea move FROM tubules back INTO the blood of the peritubular capillary network. Almost all glucose (our fuel) and amino acids (building blocks of proteins) return to the blood.

Tubular Secretion:blood to tubule

Specific substances—H+, creatinine, & drugs such as penicillin—move 

from the blood into the tubule for final waste removal and acid-base balance.

Composition of Urine

Urine comprises approximately 95% water and 5% solutes, which include:


  • Nitrogenous Wastes:Urea, uric acid, and creatinine.


  • Ions:Ammonia, sodium, and potassium.


  • Solutes Not Present in Normal Urine:Glucose, proteins, red/white blood cells, hemoglobin

Water Reabsorption

  • Approximately 99% of water that is filtered out in the glomerulus in Step 1 is reabsorbed into the blood,The Antidiuretic Hormone (ADH) released by the pituitary gland in the brain when water intake is low; ADH conserves body water by closing water channels in nephron tubules, thus reducing the loss of water in urine.

  • ADH conserves body water by closing water channels in nephron tubules, reducing the loss of water. Alcohol inhibits secretion of ADH; dehydration after drinking may contribute to the effects of a hangover

  • Caffeine increases the glomerular filtration rate and decreases tubular reabsorption of sodium, leading to increased urine production.

Functions: Kidney

  • Maintains blood pH at 7.35-7.45.

  • Efficiently removes nitrogenous waste.

  • Regulates salt and water balance, crucial for blood volume and pressure.

Kidney Function Disorders


  • Urinary Tract Infections (UTIs):Commonly caused by E. coli; symptoms may include painful urination and abdominal pain.


  • Cystitis:Inflammation of the bladder


  • Urethritis:Inflammation of the urethra


  • Pyelonephritis:Inflammation of the kidney


  • Kidney Stones: hard granules of calcium, uric acid, and proteins that form in the renal pelvis and can cause excruciating pain


  • Progressive Renal Disease:A decline in kidney function over time, often caused by diabetes, hypertension, Inherited Conditions:Such as Polycystic Kidney Disease

Treatment for Renal Failure


  • Dialysis:A medical procedure that artificially removes waste products from the blood, mimicking kidney function; patients require it several times a week. often lasts over 3 hours and is required 3 to 4 times a week.


  • Kidney Transplant:Involves replacing a diseased or damaged kidney with a healthy kidney from a donor, providing an alternative to dialysis for kidney failure patients.