Lec 20

Purpose of Male Reproductive System: To produce sperm and introduce it into the female body.
Components:
  - Urinary bladder
  - Pubic symphysis
  - Root of penis
  - Rectum
  - Ampulla of ductus deferens
  - Seminal vesicle
  - Ejaculatory duct
  - Prostate gland
  - Bulbourethral gland
  - Bulbospongiosus muscle
  - Urethra
  - Ductus (vas) deferens
  - Shaft of penis
  - Corpus cavernosum
  - Corpus spongiosum
  - Epididymis
  - Glans of penis
  - Prepuce
  - Testis
  - Scrotum

Reproductive Ducts: Pathways through which sperm passes after exiting the testes until exiting the body.
- Epididymis: A single, coiled tube approximately 6-7 meters in length, located along the top and behind the testis within the scrotum.
- Function: Sperm matures and develops motility as it passes through the epididymis, which serves as a temporary storage site, removes fluid, and provides nutrients.

Receives sperm from the epididymis and transports it from the scrotal sac through the abdominal-pelvic cavity.
Passes through the inguinal canal.
Joins the duct of the seminal vesicle to form the ejaculatory duct.

The vas deferens combines with the duct from the seminal vesicle to form the ejaculatory duct.

Semen: A mixture of sperm and secretions from accessory sex glands, averaging 3 to 5 mL per ejaculation, with about 100 million sperm per milliliter.
Seminal Vesicles:
- Function: Produce about 60% of seminal fluid volume.
- Characteristics: Secretion is yellowish, thick, and rich in fructose, which provides energy necessary for sperm motility.
Prostate Gland:
  - Shape: Doughnut-shaped, located below the bladder.
  - Function: Urethra passes through the gland; secretes seminalplasmin (antibiotic).
    - Constitutes 30% of seminal fluid volume, is thin and milk-colored, activates sperm, and is essential for ongoing sperm motility.
Bulbourethral (Cowper) Glands:
- Size and Shape: Resemble peas.
- Function: Secrete mucus-like fluid contributing less than 5% of seminal fluid volume; neutralizes acidic residues in the urethra, lubricates the urethra, and enhances external lubrication for intercourse.

Arousal: Blood flow increases, leading to the erection of the penis.
Emission: Peristaltic contractions in the ampullae of the ductus deferens push sperm into the prostatic urethra.
Ejaculation: Involves powerful, rhythmic muscular contractions.

Negative Feedback Mechanism:
  - Gonadotropin-Releasing Hormone (GnRH) is released from the Hypothalamus.
  - Anterior lobe of the pituitary gland secretes:
    - Luteinizing Hormone (LH): Stimulates interstitial endocrine cells to produce testosterone.
    - Follicle-Stimulating Hormone (FSH): Stimulates nurse cells in the testes.
Inhibin: Provides negative feedback, regulating FSH and LH secretion.

Recent studies (Levine et al., 2017) have suggested that sperm count and other semen parameters are influenced by multiple environmental factors such as:
  - Endocrine-disrupting chemicals,
  - Pesticides,
  - Heat exposure,
  - Lifestyle factors including diet, stress, smoking, and body mass index (BMI).
Implications: Sperm count can reflect impacts of modern environmental changes on male health throughout life.

Common Issues:
  - Prolonged stasis of spermatozoa in the epididymis or in transit.
  - Male accessory gland infections.
  - Environmental and lifestyle factors, including pollutants and radiation impacting spermatozoa function.
  - Possible causes of infertility and oxidative stress evaluation.
  - Systemic pathologies such as Diabetes and Cancer.
Treatment Options: Address underlying pathologies, provide antioxidant supplementation, and avoid factors that promote reactive oxygen species (ROS).

Introduction to the Urinary System:
  - Consists of:
    - Two kidneys,
    - Two ureters,
    - Urinary bladder,
    - Urethra.
Functions:
  - Adjusting blood volume and blood pressure.
  - Regulating plasma concentrations of ions (sodium, potassium, chloride).
  - Stabilizing blood pH.
  - Conserving valuable nutrients.
  - Removing drugs and toxins from the bloodstream.
  - Stimulating glucose production.
  - Stimulating red blood cell production.

Kidney Anatomy:
  - Renal artery and renal vein are major blood vessels.
  - Diaphragm, aorta, and inferior vena cava in proximity.
  - The kidney is typically located around vertebra L2.
Landmarks:
  - Renal cortex (outer region),
  - Renal medulla (inner region),
  - Renal pyramids (cone-shaped structures),
  - Renal columns (between pyramids),
  - Hilum (indentation where vessels enter and exit).

Urea Formation:
- Proteins break down into amino acids, leading to the removal of the amine group, forming ammonia (NH3).
- The liver converts ammonia to urea.
Other Nitrogenous Wastes:
- Uric acid (from nucleic acid catabolism),
- Creatinine (from creatine phosphate breakdown).
Definition of Waste: Any substance that is useless to the body or present in excess.
Metabolic Waste: Waste produced by bodily processes.

Types of Nephrons:
- Cortical Nephrons: 85% of nephron population, primarily located in the cortex, responsible for most regulatory functions.
- Juxtamedullary Nephrons: 15% of nephrons, involved in concentrated urine formation.
Main Parts of Nephron:
- Renal Corpuscle: Responsible for filtration.
- Renal Tubule: Involved in reabsorption and secretion.
Glomerular Filtration: Creates plasma-like filtrate of blood.

Glomerular Filtration: Water and dissolved substances filter out of glomeruli into Bowman capsule. The Normal Glomerular Filtration Rate (GFR) is $125 ext{ mL/min}$ .
Tubular Reabsorption: Returns useful solutes from filtrate back into the blood.
Tubular Secretion: Adds wastes from blood to the filtrate.
Water Conservation: Returns water from urine back to blood.

Forces Involved in Filtration:
  1. Blood Hydrostatic Pressure (BHP): 60 mm Hg out.
  2. Colloid Osmotic Pressure (COP): -32 mm Hg in.
  3. Capsular Pressure (CP): -18 mm Hg in.
Net Filtration Pressure (NFP): Calculated as:
$ext{NFP} = ext{BHP} - ext{COP} - ext{CP} = 60 - 32 - 18 = 10 ext{ mm Hg out}$ .
Regulation Mechanisms: Three homeostatic mechanisms control GFR:
  - Renal autoregulation,
  - Sympathetic control,
  - Hormonal control.

Function: Reabsorbs approximately 65% of glomerular filtrate, consuming about 6% of resting ATP and calories.
Mechanism:
- Removes some substances from the blood and secretes them into tubular fluid for disposal.
- The reabsorption of solutes creates hypertonic conditions in tubule cells and tissue fluid, leading to water reabsorption via osmosis (obligatory water reabsorption).

Sodium (Na+) Reabsorption: Key to creating osmotic and electrical gradients that drive the reabsorption of water and other solutes.
Transport Maximum: Limited by the number of transporters in tubule cell membranes and solute transport can lead to excess appearing in urine when transporters are saturated. For instance, blood glucose levels exceeding $220 ext{ mg/dL}$ result in glycosuria (glucose in the urine).