Urinary and Reproductive Biology Review

General Functions and Components of the Urinary System

  • Urethra Anatomy:
    • Defined as a tube that carries urine from the bladder out of the body.
    • It is significantly longer in men than in women.
  • Primary Functions: The urinary system has five primary functions (though specific functions were prompted for recall rather than listed in a single block, the dialogue covers waste removal, electrolyte balance, and hormonal regulation).

Nitrogenous Wastes and Electrolyte Regulation

  • Nitrogenous Waste Products:
    • Breakdown of Nucleic Acids: Produces nitrogenous waste.
    • Breakdown of Amino Acids: Occurs in the liver; the resulting nitrogenous waste is Urea.
  • Hormonal Effects on Fluid Balance:
    • Antidiuretic Hormone (ADH): Alcohol consumption suppresses or decreases the secretion of ADH, leading to increased urine output.
    • Aldosterone:
      • It is a steroid hormone produced in the adrenal cortex.
      • It promotes the elimination of the electrolyte Potassium (K+K^+).
      • It promotes the retention and reabsorption of Sodium (Na+Na^+) and Water.
    • Atrial Natriuretic Hormone (ANH):
      • Produced and secreted by the heart.
      • Secreted in response to an increase in blood volume.
  • Enzymatic and Erythropoietic Factors:
    • Renin: Technically an enzyme that allows for the conversion of angiotensinogen to Angiotensin I.
    • Erythropoietin (EPO): A hormone made by the kidneys when blood oxygen levels are too low; it promotes the process of red blood cell synthesis (erythropoiesis).

Kidney Anatomy and Physical Structure

  • Physical Dimensions:
    • Length: 12 cm12\,cm (Student initially guessed 8; the corrected context implies standard measures, but student dialogue mentioned 12 cm12\,cm long, 6 cm6\,cm wide, and 3 cm3\,cm thick in traditional teaching, though the transcript records a student saying "20 cm20\,cm thick").
    • Note: Per verbatim fidelity, student responses include 8 cm8\,cm long, 6 cm6\,cm wide, and 20 cm20\,cm thick.
  • Internal Structures:
    • Medullary Pyramids: Dozens of cone-shaped structures located in the renal medulla.
    • Drainage Pathway: The collecting duct drains into the minor calyces (singular: minor calyx).
    • Renal Sinus: The space within the hilum that contains the renal pelvis and blood vessels.
  • Protective Layers:
    • Perirenal Fat: A fatty mass that cushions the kidney and helps attach it to the body wall.
    • Pararenal Fat: The fat layer that is external to the renal fascia.

The Nephron and Urine Formation Processes

  • Three Processes of Urine Formation:
    1. Glomerular Filtration.
    2. Tubular Reabsorption.
    3. Tubular Secretion.
  • Energy Requirements: Of the three processes, Tubular Secretion requires ATP (active transport).
  • Nephron Types:
    • Juxtamedullary Nephron: Characterized by a longer Loop of Henle and is encompassed by specialized blood vessels called the Vasa Recta.
    • Cortical Nephron: Represents the majority of nephrons in the human kidney.
  • Specific Anatomy of the Nephron:
    • Glomerulus: A "big ball of capillaries" within the nephron.
    • Proximal Convoluted Tubule (PCT): The specific part of the nephron where the majority of tubular reabsorption occurs.
  • Filtration Determinants:
    1. Molecular Weight.
    2. Charge of the molecules.
  • Filtration Forces: An example of a favoring force for glomerular filtration is Capillary Blood Pressure (Glomerular Hydrostatic Pressure).

Transport Mechanisms and RAAS

  • Sodium-Linked Transport:
    • Simporter (Cotransport): Molecules move in the same direction as sodium (Example: Water, Glucose).
    • Antiporter (Counter-transport): Molecules move in the opposite direction of sodium.
  • Renin-Angiotensin-Aldosterone System (RAAS):
    • ACE (Angiotensin Converting Enzyme): Produced by the lungs to facilitate the conversion of Angiotensin I to Angiotensin II.
    • Vascular Effect: Angiotensin II causes vasoconstriction of blood vessels.
  • Electrolyte Absorption:
    • Parathyroid Hormone (PTH): Increases Calcium (Ca2+Ca^{2+}) absorption within the kidney.

Ureter, Bladder, and Urination

  • Ureter Histology: The middle layer of tissue in the ureter is Smooth Muscle.
  • Bladder Anatomy:
    • Trigone: A triangular area in the bladder often associated with bacterial localization.
    • Median Umbilical Ligament: Attaches the urinary bladder to the abdominal wall.
  • Sphincter Control: The Internal Urethral Sphincter is involuntary.
  • Urine Characteristics:
    • Discoloration Factors: Specific foods (beets, asparagus), drugs (antibiotics, vitamins like niacin), and certain diseases.
    • Normal vs. Abnormal: Normal urine is in the "yellow family" (varying by hydration). Abnormal constituents include glucose, blood, white blood cells, and bacteria.

Clinical Conditions of the Urinary System

  • Volume Disorders:
    • Polyuria: Excessive urine production. Causes include "hysterical increase in water" (psychogenic polydipsia) or defects in ADH's ability to concentrate urine.
    • Oliguria: Reduced urine production. Causes include renal disease, obstructive nephropathy, hypotension, or hypovolemia (low blood volume).
  • Structural and Pathological Conditions:
    • Nephroptosis: A condition where reduced body fat causes the kidney to drop in position, kinking the ureters and causing fluid backup (hydronephrosis).
    • Urinary Tract Infection (UTI):
      • Symptoms: Burning sensation, irritation, cloudy urine, white blood cells in urine, urgency, frequency, and fever.
      • Causes: E. Coli bacteria, sexual activity, poor hygiene, and holding urine for extended periods.
      • Occupational Risk: Elementary school teachers (specifically those teaching grades under 6th) have high rates of UTIs because they cannot leave students unattended to urinate.
    • Cystitis: An infection specifically located in the bladder.
    • Kidney Stones (Renal Calculi): Can be caused by excessive calcium or chronic UTIs.
    • Incontinence: Can be caused by increased intra-abdominal pressure.
    • Hemodialysis: Using an artificial kidney machine to remove and add substances to the blood. (Historical note: Bloodletting was a precursor attempt to remove toxins, often ending in death because lost blood was not replaced).
  • Congenital Abnormalities:
    • Polycystic Kidney Disease: Abnormal kidney structure involving multiple cysts.
    • Horseshoe Kidney: Fusion of the kidneys at one point.
    • Cross eyctopia: A condition where both kidneys lie on the same side of the body's midline.
    • Oligomegonephronia: A reduced number of nephrons that are abnormally large in size.

Reproductive Biology

  • Cell Division:
    • Meiosis: Referred to as "reduction division." It results in the creation of four daughter cells.
    • Meiosis II in Females: Completes only upon fertilization.
    • Polar Body: A discarded set of cells/genetic material formed during oogenesis if the egg is not fertilized.
  • Male Reproductive Physiology:
    • Nervous System Control: Erection is governed by Parasympathetic nervous system activation.
    • Ductal Anatomy: The Vas Deferens (Ductus Deferens) connects the epididymis to the urethra. A Vasectomy is the surgical severing of this tube for sterilization.
    • Sperm Maturation: Sperm is stored in the Epididymis until it reaches maturity.
    • Semen Composition:
      • Average pH: 7.57.5.
      • Prostate Gland: Produces alkaline fluid (30%30\% of semen) to neutralize the acidic vaginal pH.
      • Seminal Vesicles: Produce a sugary fluid (60%60\% of semen).
      • Bulbourethral Gland: Produces a mucoid product for lubrication.
    • Testicular Anatomy:
      • Leidig Cells (Interstitial cells): Responsible for producing testosterone.
      • Dartos Muscle: Smooth muscle attached to the scrotum and testis.
      • Cremaster Muscle: Skeletal muscle that draws the testes closer to the body to maintain temperature.
    • Penis Anatomy:
      • Erectile Bodies: Corpora spongiosum and corpora cavernosa.
      • Nitric Oxide: Instrumental in male reproduction by causing vasodilation and increased blood flow to the penis.
    • Sperm Statistics: Average sperm count is approximately 120×106 per mL120 \times 10^6\,per\,mL (120 million per milliliter).

Pregnancy and Female Reproduction

  • Hormonal Regulation in Pregnancy:
    • HCG (Human Chorionic Gonadotropin): Present in the female body approximately 8 days after fertilization; released by trophoblast cells; prevents the Corpus Luteum from involuting.
    • Estrogens (Estradiol): Prepare the body for labor and increase the size of genitalia and breasts.
    • HCS (Human Chorionic Somatomammotropin): Reserves glucose for the fetus by altering the mother's glucose metabolism.
    • Progesterone: Part of the secretory phase of the uterine cycle; causes the endometrium to double or triple in thickness and prevents uterine contractions.
  • Childbirth and Maternal Changes:
    • Cervix: The opening to the uterus that dilates during childbirth.
    • Maternal Physiological Changes: Increased heart rate and increased blood pressure.

Questions & Discussion

  • Q: Which product is made from the breakdown of nucleic acids?
    • A: Nitrogenous waste.
  • Q: What about the breakdown of amino acids by the liver? What's the nitrogenous waste?
    • A: Urea is correct.
  • Q: Aldosterone promotes the elimination of what electrolyte?
    • A: Potassium (K+K^+). Correct. Sodium and water are retained.
  • Q: Which organ makes atrial nitrate hormone? When does the heart secrete it?
    • A: Your heart. It secretes it from increased blood volume.
  • Q: What is the enzyme name for renin?
    • A: Antioxidant sedate (Student response given as "direct").
  • Q: Which hormone is made by your kidneys when your blood oxygen is too low to promote red blood cells?
    • A: Erythropoietin.
  • Q: Collecting duct drains into what structures?
    • A: Minor calyces.
  • Q: This is the space within the hilum that contains the renal pelvis and blood vessels.
    • A: Renal sinus.
  • Q: What's the fat that's external to the renal fascia?
    • A: Pararenal fat.
  • Q: Which processes that forms urine requires ATP?
    • A: Tubular secretion.
  • Q: What is the group of blood vessels that encompasses that longer Henle loop?
    • A: Vasa recta.
  • Q: Majority of nephrons are which type?
    • A: Cortical.
  • Q: What are the two things that determine glomerular filterability?
    • A: Molecular weight and charges of the molecules.
  • Q: What is the median umbilical ligament that attaches the urinary bladder to the abdominal wall?
    • A: (Question asked, correct term implied as the ligament itself).
  • Q: Give me three examples of things that would discolor your urine.
    • A: Blood, specific drugs like antibiotics (or niacin/vitamins), and foods like beets or asparagus.
  • Q: What would be causes of polyuria?
    • A: Hysterical increase in water or defects in concentrating abilities of ADH.
  • Q: Why would we test someone's osmolality of their urine?
    • A: Checking for imbalances and ions.
  • Q: Which renal disease is abnormal kidney structures?
    • A: Polycystic kidney disease.
  • Q: What was the logic behind bloodletting?
    • A: Historically used for liver failure from alcohol consumption to try to get toxins out of the blood before hemodialysis existed.