Lecture Notes: Urinary System and Endocrine System Overview

Key Hormones and Urinary System Function

Antidiuretic Hormone (ADH)

• ADH acts on collecting ducts to absorb water.
• Reduction in ADH leads to Diabetes Insipidus:
  • Results in excessive urination (diuresis).
  • "Diabetes" means "to pass through," referring to water in this context.
  • Contrast with Diabetes Mellitus (sugar passing through).

Nephron and Collecting Duct Pathway

• Urine formed in nephron, moves through kidney structures:
  • Pyramids in the medulla collect from nephrons.
  • Urine exits kidney via calyces:
    • Minor Calyces receive from pyramids.
    • Major Calyces form from minor calyces.
  • Renal pelvis collects urine to ureter.

Ureter Function

• Ureter length: 10 - 12 inches.
• Lined with transitional epithelium (changes shape with urine flow).
• Contains two smooth muscle layers.
• Urine flow is not continuous; it moves in intervals (contractions every 2-3 minutes).

Bladder and Urethra Anatomy

Urinary Bladder

• Hollow organ, lined with transitional epithelium.
• Contains detrusor muscle with stretch receptors signaling when to urinate.
• Capacity: 700-800 cc.
• Trigone region formed by ureter entries and urethra exit.

Urethra Differences Between Genders

• Female Urethra:
  • ~1.5 inches long.
  • Surrounded by smooth muscle (internal sphincter).
  • External sphincter (skeletal muscle) controls urination.
• Male Urethra:
  • ~7-8 inches long.
  • Divided into prostatic, membranous, and cavernous sections.
  • Internal sphincter (prevents dripping), external sphincter (voluntary control).

Introduction to the Endocrine System

Overview

• Composed of ductless glands with rich blood supply.
• Glands secrete hormones targeting specific organs.

Major Endocrine Glands

• Pineal Gland: Regulates circadian rhythm, produces melatonin.
• Ovaries and Testes: Produce hormones like estrogen, progesterone, and testosterone.
• Thyroid Gland: Located over trachea, produces thyroid hormones.
• Parathyroid Gland: Regulates calcium with osteoclast activity.
• Adrenal Gland: Produces aldosterone, affects kidney function.
• Pituitary Gland: Acts as the master gland, controlling other endocrine glands.

Detailed Gland Functions

• Pineal Gland: Melatonin production, affects gonadal development.
• Thyroid Gland: Bi-lobed, connected by isthmus, plays a critical role in metabolism.

Visual Aids (Slides Reviewed)

• Slides included views of the ureter, urinary bladder, male urethra, pineal gland, ovary, testes, and thyroid gland.

Important Notes

• Transitional epithelium adapts to volume changes in ureters and bladder.
• Male urethra serves dual purposes (urination and sperm transport).
• Unique cellular structure of thyroid gland to be discussed further.