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Nervous System Summary, Summaries of Anatomy

Nanyang Technological UniversityAnatomy

This is about nervous system. Summary for reviewer

Typology: Summaries

2024/2025

Uploaded on 11/21/2025

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URINARY SYSTEM
URINARY SYSTEM AND FLUID BALANCE
FUNCTIONS OF THE URINARY SYSTEM
EXCRETION
- metabolic by products from intestines, skin,
liver, lungs (nitrogenous wastes, toxins, drugs,
excess ions)
REGULATION OF BLOOD VOLUME AND
PRESSURE
- Kidneys control the ECF volume through
production of diluted urine or small volume of
concentrated urine
- Control of renin
REGULATION OF CONCENTRATION OF SOLUTES
IN THE BLOOD
- Regulates concentration of glucose, Na, Cl, K,
Ca, HCO3
REGULATION OF ECF pH
- Secretion of H to regulate pH
REGULATION OF RBC SYNTHESIS
- Secretes erythropoietin, a hormone regulating
the synthesis of RBC in bone marrow
VIT D SYNTHESIS
- Controls Ca blood level
- Converts Vit D to its active form
ORGANS AND STRUCTURES IN THE URINARY
SYSTEM
➢ KIDNEYS
➢ URETERS
➢ URINARY BLADDER
➢ URETHRA
KIDNEYS
KIDNEYS: LOCATION
● The kidneys are in retroperitoneal position
● The kidneys are situated at the level of the T12
to L3 vertebrae
● The right kidney is slightly lower than the left
because of position of the liver
KIDNEY: STRUCTURE
● An adult kidney is about 12 cm (5 in) long and
6 cm (2.5 in) wide
● Bean shaped organs
● Size of a tightly clenched fist
● adrenal gland sits atop each kidney
KIDNEY: PARTS
✓ Three PROTECTIVE LAYERS enclose the kidney
o Renal fascia
● is the most superficial fat layer that anchors the
kidney and adrenal gland to surrounding
structures
● Composed of anterior and posterior
○ Fibrous capsule
● encloses each kidney
○ Perirenal fat capsule
● surrounds the kidney and cushions against
blows
✓ Renal hilum
● A medial indentation where several
structures enter or exit the kidney
(ureters, renal blood vessels, and
nerves)
✓ Renal Sinus
● Cavity/ Opening containing the blood
vessels and fat
✓ Three regions revealed in a longitudinal section
o Renal cortex—outer region
o Renal medulla—deeper region
- Renal medullary pyramids—triangular regions
of tissue in the medulla
- Renal columns—extensions of cortex-like
material that separate the pyramids
o Renal pelvis—medial region that is a flat,
funnel-shaped tube
- Composed of major and minor calyces
- Calyces form cup-shaped “drains” that enclose
the renal pyramids
- Calyces collect urine and send it to the renal
pelvis, on to the ureter, and to the urinary
bladder for storage
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URINARY SYSTEM AND FLUID BALANCE

FUNCTIONS OF THE URINARY SYSTEM

EXCRETION

  • metabolic by products from intestines, skin, liver, lungs (nitrogenous wastes, toxins, drugs, excess ions) REGULATION OF BLOOD VOLUME AND PRESSURE
  • Kidneys control the ECF volume through production of diluted urine or small volume of concentrated urine
  • Control of renin REGULATION OF CONCENTRATION OF SOLUTES IN THE BLOOD
  • Regulates concentration of glucose, Na, Cl, K, Ca, HCO REGULATION OF ECF pH
  • Secretion of H to regulate pH REGULATION OF RBC SYNTHESIS
  • Secretes erythropoietin, a hormone regulating the synthesis of RBC in bone marrow VIT D SYNTHESIS
  • Controls Ca blood level
  • Converts Vit D to its active form ORGANS AND STRUCTURES IN THE URINARY SYSTEM ➢ KIDNEYS ➢ URETERS ➢ URINARY BLADDER ➢ URETHRA KIDNEYS KIDNEYS: LOCATION ● The kidneys are in retroperitoneal position ● The kidneys are situated at the level of the T to L3 vertebrae ● The right kidney is slightly lower than the left because of position of the liver

KIDNEY: STRUCTURE

● An adult kidney is about 12 cm (5 in) long and 6 cm (2.5 in) wide ● Bean shaped organs ● Size of a tightly clenched fist ● adrenal gland sits atop each kidney KIDNEY: PARTS ✓ Three PROTECTIVE LAYERS enclose the kidney o Renal fascia ● is the most superficial fat layer that anchors the kidney and adrenal gland to surrounding structures ● Composed of anterior and posterior ○ Fibrous capsule ● encloses each kidney ○ Perirenal fat capsule ● surrounds the kidney and cushions against blows ✓ Renal hilum ● A medial indentation where several structures enter or exit the kidney (ureters, renal blood vessels, and nerves) ✓ Renal Sinus ● Cavity/ Opening containing the blood vessels and fat ✓ Three regions revealed in a longitudinal section o Renal cortex —outer region o Renal medulla —deeper region

  • Renal medullary pyramids —triangular regions of tissue in the medulla
  • Renal columns —extensions of cortex-like material that separate the pyramids o Renal pelvis —medial region that is a flat, funnel-shaped tube
  • Composed of major and minor calyces
  • Calyces form cup-shaped “drains” that enclose the renal pyramids
  • Calyces collect urine and send it to the renal pelvis, on to the ureter, and to the urinary bladder for storage

KIDNEY: BLOOD SUPPLY

✓ Arterial Blood Supply

  • One-quarter of the total blood supply of the body passes through the kidneys each minute
  • Renal artery provides each kidney with arterial blood supply
  • Renal artery divides into segmental arteries → arcuate arteries → interlobar arteries → cortical radiate arteries ✓ Venous blood flow
  • Cortical radiate veins →arcuate veins → interlobar veins → renal vein
  • There are no segmental veins
  • Renal vein returns blood to the inferior vena cava KIDNEY: NEPHRONS ✓ Structural and functional units of the kidneys ✓ Each kidney contains over a million nephrons ✓ Each nephron consists of two main structures ✓ Parts:
  • Renal corpuscle consists of: ● Glomerulus ● Glomerular (Bowman’s) capsule - Renal tubules subdivisions: ● Proximal convoluted tubule (PCT) ● Nephron loop (loop of Henle) ● Distal convoluted tubule (DCT) RENAL CORPUSCLE consists of: ● Glomerulus
  • a knot of capillaries made of podocytes which makes up the inner layer of the glomerular capsule
  • Foot processes cling to the glomerulus
  • Filtration slits create a porous membrane—ideal for filtration ● Glomerular (Bowman’s) capsule
  • a cup-shaped structure that surrounds the glomerulus
  • First part of the renal tubule

RENAL TUBULES

● Extends from glomerular capsule and ● ends when it empties into the collecting ● duct ● From the glomerular (Bowman’s) capsule, ● the subdivisions of the renal tubule are: ● Proximal convoluted tubule (PCT) ● Nephron loop (loop of Henle) ● Distal convoluted tubule (DCT) KIDNEY: NEPHRONS BASED ON LOCATION ✓ Cortical nephrons ▪ Located entirely in the cortex ▪ Include most nephrons ✓ Juxtamedullary nephrons ▪ Found at the cortex-medulla junction ▪ Nephron loop dips deep into the medulla KIDNEY: COLLECTING DUCTS ❖ Collecting ducts

  • collect urine from both types of nephrons, through the renal pyramids, to the calyces, and then to the renal pelvis KIDNEY: TWO CAPILLARY BEDS ASSOCIATED WITH EACH NEPHRON ✓ Glomerulus ▪ Fed and drained by arterioles ● Afferent arteriole —arises from a cortical radiate artery and feeds the glomerulus ● Efferent arteriole —receives blood that has passed through the glomerulus ▪ Specialized for filtration ▪ High pressure forces fluid and solutes out of blood and into the glomerular capsule ✓ Peritubular capillary beds ● Arise from the efferent arteriole of the glomerulus ● Low-pressure, porous capillaries ● Adapted for absorption instead of filtratio ● Cling close to the renal tubule to receive solutes and water from tubule cells ● Drain into the interlobar veins
  1. Capsular Hydrostatic Pressure (CHP) : 10 mm Hg (inward)
  2. Blood Colloid Osmotic Pressure (BCOP): 30 mm Hg (inward) ☆ Net Filtration Pressure (NFP): GCP – CHP - BCOP = 10 mm Hg Clinical Insight – Glomerulonephritis
    • kidney disorder where inflammation and damage occur in the glomeruli Etiology : •Infections : Post-infectious glomerulonephritis can occur after strep throat, skin infections, or other bacterial or viral infections •Autoimmune Diseases : Conditions like systemic lupus erythematosus (SLE), vasculitis •Other Causes : Drugs, toxins, certain cancers, and genetic factors Pathophysiology :
  • Inflammation of glomeruli leading to damage to the filtering structures
  • Increased Permeability of Filtration membrane allowing protein blood cells to leak into the urine
  • Fluid Retention due to the kidney’s struggle to regulate fluid balance , leading to swelling (edema) in the face, legs, lungs and other areas
  • High Blood Pressure Signs and Symptoms : ● Swelling (Edema) ● High Blood Pressure (Hypertension) ● Blood in the Urine (Hematuria): Urine may appear pink, brown, or cola-colored. ● Protein in the Urine (Proteinuria): Urine may appear foamy or bubbly. ● Decreased Urine Output ● from Other Symptoms: Fatigue, nausea, loss of appetite, joint pain, and weakness can also occur Regulation of Glomerular Filtration Rate (GFR) •GFR remains stable between 90–180 mm Hg MAP •Maintained by autoregulation •Drops significantly during hemorrhage or severe dehydration Regulation of Glomerular Filtration Rate (GFR): Autoregulation TWO MECHANISMS OF AUTOREGULATION: 1. Myogenic Mechanism •Afferent arteriole smooth muscle detects stretch •↑ BP → Stretch → Vasoconstriction •↓ BP → Relaxation → Vasodilation 2. Tubuloglomerular Feedback •Based on filtrate flow past macula densa •↑ Filtrate flow → Macula densa signals afferent arteriole → Vasoconstriction •↓ Glomerular capillary pressure → ↓ GFR Regulation of Glomerular Filtration Rate (GFR): Sympathetic Stimulation •Mild stimulation → Little effect •Intense stimulation (e.g., shock, exercise) → - Vasoconstriction of renal vessels - ↓ Renal blood flow & ↓ GFR Glomerular Filtration Rate in Shock & Stress •Intense vasoconstriction → Minimal urine formation •Long-term ↓ blood flow → Kidney damage •Short-term ↓ blood flow → Protective (homeostatic) Summary •GFR stable due to autoregulation •Myogenic & tubuloglomerular feedback are key •Sympathetic activity reduces GFR under stress •Prolonged reduction in flow → renal damage 2 .TUBULAR REABSORPTION •Return of water and solutes from filtrate to blood •Approximately 99% of filtrate is reabsorbed •Essential for maintaining fluid and electrolyte balance •Prevents loss of vital nutrients Mechanisms of Reabsorption •Passive Transport: Diffusion, Osmosis •Active Transport: Requires ATP •Secondary Active Transport: Coupled with Na+ movement •Facilitated Diffusion: Carrier proteins assist Mechanisms of Reabsorption: Proximal Convoluted Tubule (PCT) •Reabsorbs ~65% of filtrate volume

•Reabsorbed substances: Na+, K+, Cl−, HCO₃−, glucose, amino acids •Water follows solutes via osmosis •Utilizes Na+/K+ ATPase pumps Mechanisms of Reabsorption: Loop of Henle Descending Limb: •Permeable to water •Water exits, filtrate becomes concentrated Ascending Limb: •Impermeable to water •Na+, K+, Cl− actively reabsorbed •Filtrate becomes dilute Mechanisms of Reabsorption: Distal Convoluted Tubule (DCT) and Collecting Duct Reabsorbs Na+, Cl−, and Ca2+ Under hormonal control: Aldosterone and ADH ADH increases water permeability Fine-tunes electrolyte and fluid balance Mechanisms of Reabsorption: Urea and Other Solutes •Urea: ~50% passively reabsorbed •Creatinine, uric acid: minimally reabsorbed •Concentration increases as water is reabsorbed •Eliminated to prevent toxicity Summary •Tubular reabsorption is vital for conserving essential substances •Different nephron segments specialize in reabsorbing specific substances •Hormonal regulation ensures adaptability to the body's needs •Efficient reabsorption maintains homeostasis and prevents dehydration

3. TUBULAR SECRETION •Movement of substances from blood → filtrate •Removes: **_- Metabolic by-products

  • Drugs & toxins_** •Ions (e.g., H⁺, K⁺) •Occurs in PCT & DCT •Involves active and passive transport TUBULAR SECRETION: Substances Secreted Actively Secreted: •H⁺ •K⁺ •Penicillin •PAH (para-aminohippuric acid) Passively Secreted: •Ammonia (NH₃): Peritubular capillaries → tubule cells → lumen TUBULAR SECRETION: Ammonia Secretion •Ammonia (NH ₃ ): by-product of amino acid metabolism •Produced by renal tubule epithelial cells •Diffuses into the tubular lumen •Helps buffer excess H ⁺ TUBULAR SECRETION : Antiport Mechanism – H ⁺ and Na ⁺ ● Antiport (exchange):
  • Na⁺ enters tubule cell
  • H⁺ secreted into lumen ● Driven by Na ⁺ gradient ● Maintains pH balance TUBULAR SECRETION : H ⁺ Generation and Secretion
  • CO₂ + H₂O → H⁺ + HCO₃⁻ (via carbonic anhydrase) •H⁺: Secreted into tubule lumen •HCO₃⁻: Reabsorbed into peritubular capillaries •Helps regulate blood pH TUBULAR SECRETION : Functional Significance Eliminates: ● Waste products not filtered ● Excess ions (H⁺, K⁺) ● Drugs and toxins ● Maintains pH homeostasis ● Fine-tunes filtrate composition Summary ● Tubular secretion = blood → tubule lumen ● Removes wastes, drugs, and excess ions ● Uses active and passive mechanisms ● iCrucial for pH regulation and detoxification
  • Increases urine volume, reducing blood volume and pressure. Summary •Kidney Regulation:
    • Balances urine concentration and volume through hormonal and neural mechanisms. •Hormonal Controls:
    • RAAS and ADH conserve water and sodium.
    • ANH promotes excretion of water and sodium. •Homeostasis :
    • These systems work together to maintain fluid and electrolyte balance. KIDNEY: URINE CHARACTERISTICS Normal Characteristics of Urine: •Color : Clear and pale to deep yellow
    • Due to urochrome, a pigment from hemoglobin breakdown •Clarity: Transparent when freshly voided •Odor : Slightly aromatic; develops ammonia scent over time •pH : Slightly acidic (~6), but can range 4.5– •Specific Gravity : 1.001–1.
    • Indicates urine concentration •Sterility : Sterile at formation (in the kidneys) Note: Pale straw color indicates dilute urine; deeper yellow indicates concentration. KIDNEY: SOLUTES IN NORMAL URINE •Electrolytes :
    • Sodium (Na ⁺ ) and Potassium (K ⁺ ) – regulate fluid balance and nerve/muscle function •Nitrogenous Wastes:
    • Urea – from amino acid breakdown
    • Uric Acid – from nucleic acid metabolism
    • Creatinine – from muscle metabolism •Other Solutes :
    • Ammonia (NH ₃ ) – formed from protein metabolism
    • Bicarbonate (HCO ₃⁻ ) – helps regulate acid-base balance These solutes reflect kidney filtration and overall metabolic activity. KIDNEY: SOLUTES NOT NORMALLY FOUND IN URINE •Glucose – Indicates possible diabetes mellitus •Blood Proteins (e.g., albumin) – May suggest kidney damage •Red Blood Cells (RBCs) – Sign of trauma, infection, or stones •Hemoglobin – May result from hemolytic anemia •White Blood Cells (WBCs/pus) – Indicates urinary tract infection (UTI) •Bile Pigments – Associated with liver disease or bile duct blockage Presence of these substances often signals underlying pathology. URETERS •Slender muscular tubes: 25–30 cm (10–12 inches) •Connect renal pelvis to urinary bladder •Enter the posterior aspect of the bladder •Travel behind the peritoneum •Peristalsis assists gravity in moving urine URINARY BLADDER •Smooth, collapsible, muscular sac behind the pubic symphysis •Temporarily stores urine Parts: •Trigone: Triangular area formed by:
      • 2 ureteral openings
      • 1 internal urethral orifice •In males, prostate surrounds the bladder neck •Capacity:
  • ~500 ml = moderately full
  • Max ~1000 ml URETHRA
  • Thin-walled tube that expels urine from bladder to outside via peristalsis Function:
  • Females: Carries urine only •Males: Carries both urine and sperm Length:
  • Females: 3–4 cm (1.5 in) •Males: 20 cm (8 in) Location:
  • Females: Anterior to vaginal opening •Males: Passes through:
  • Prostatic urethra
  • Membranous urethra
  • Spongy urethra Sphincters controlling urination: •Internal urethral sphincter : Involuntary, smooth muscle
  • External urethral sphincter : Voluntary, skeletal muscle MICTURITION Micturition: The Urination Process
  • Voiding or emptying of the urinary bladder - Initiation :
  • Stretch receptors in bladder wall send signals to sacral spinal cord
  • Reflex impulses return via pelvic splanchnic nerves → bladder contracts
  • Urge to void:
  • Urine pushed past involuntary internal sphincter
  • Reaches upper urethra
  • Control :
  • External urethral sphincter is voluntary
  • Micturition can be delayed consciously BODY FLUID COMPARTMENT Body Water Content by Age & Sex •Babies : ~75% •Young adult males: ~60% •Young adult females: ~50% •Elderly : ~45–50% •Water is essential for numerous physiological functions •Fluid balance is tightly regulated Body Fluid Compartments •Intracellular Fluid (ICF)
  • Inside cells
  • ~⅔ of total body water •Extracellular Fluid (ECF)
  • Outside cells
  • Includes: ● Interstitial fluid (IF) ● Blood plasma ● Lymph ● Transcellular fluids (e.g., cerebrospinal, synovial) •Plasma
  • Subdivision of ECF
  • ~3 liters of total body water

Buffer Systems (act quickly) •Bicarbonate, Phosphate, Protein buffers •Neutralize excess H+ or OH− to stabilize pH Respiratory Control •↑ Respiration = ↓ CO₂ = ↑ pH •↓ Respiration = ↑ CO₂ = ↓ pH Renal Control •If pH rises:

  • Excrete bicarbonate , retain H ⁺ •If pH drops:
  • Reabsorb bicarbonate , excrete H ⁺ DEVELOPMENTAL ASPECTS OF THE URINARY SYSTEM Fetal Development of the Kidneys •Kidney development begins early in embryonic life •Functional urine production by third month of fetal life Pediatric Concerns •Urinary system problems in children include:
  • Infections from fecal bacteria
  • STIs in adolescents
  • Streptococcus-related issues •Voluntary sphincter control begins ~18 months •Nighttime bladder control may take until age 4 Common Urinary Disorders Before Adulthood •UTIs most common urinary issue before old age •E. coli is responsible for ~80% of UTIs •Symptoms: dysuria, urgency, and sometimes fever Renal Failure in Younger Adults •Rare but serious •Kidneys cannot concentrate urine •Requires dialysis for blood chemical balance Aging and the Urinary System •Filtration rate decreases with age •Tubules lose efficiency •Results in urgency, frequency, incontinence Male-Specific Aging Concerns •Urinary retention is common •Often due to prostate gland enlargement

Summary of Urinary Aging Issues •Urgency : Sudden need to urinate •Frequency : Frequent urination, small amounts •Nocturia : Nighttime urination •Incontinence : Loss of bladder control •Urinary Retention : Incomplete emptying, especially in males Conclusion •Urinary development begins early in life •Control and function evolve through childhood •Aging brings functional decline and common issues •Nurses play a critical role in detection and management