The Urinary System

Overview of the Urinary System

The urinary system is responsible for filtering blood, removing waste, and regulating fluid and electrolyte balance. It consists of several organs that work together to produce, store, and eliminate urine.

• Kidneys: Bean-shaped organs that filter blood and form urine.

• Ureters: Tubes that transport urine from the kidneys to the urinary bladder.

• Urinary Bladder: A muscular sac that stores urine until excretion.

• Urethra: The tube through which urine is expelled from the body.

Kidney Anatomy

• Capsule: The tough, fibrous outer covering of the kidney.

• Hilus (Hilum): The medial indentation where blood vessels, nerves, and the ureter enter/exit the kidney.

• Cortex: The outer region of the kidney, containing renal corpuscles and parts of the renal tubules.

• Medulla: The inner region, organized into renal pyramids.

• Renal Pyramid: Triangular structures in the medulla; each has a base (faces cortex) and an apex/papilla (points toward the renal pelvis).

• Renal Column: Extensions of cortical tissue between pyramids.

• Minor Calyx: Collects urine from a single pyramid.

• Major Calyx: Formed by the convergence of minor calyces.

• Renal Pelvis: Funnel-shaped structure that collects urine from major calyces and channels it into the ureter.

• Arteries:

  • Renal artery: Supplies blood to the kidney.

  • Interlobar arteries: Run between pyramids.

  • Arcuate arteries: Arch over the base of pyramids.

  • Cortical radiate arteries: Extend into the cortex.

Microscopic Anatomy of the Kidney

• Glomerulus: A tuft of capillaries involved in filtration.

• Glomerular (Bowman's) Capsule: Surrounds the glomerulus and collects filtrate.

• Renal Tubule: Includes the proximal convoluted tubule, nephron loop (loop of Henle), distal convoluted tubule, and collecting duct.

Structural and Functional Unit

• The nephron is the structural and functional unit of the kidney, responsible for urine formation.

Urine Formation: Three Sub-Processes

1. Glomerular Filtration: Blood pressure forces water and solutes out of the glomerulus into the glomerular capsule.

2. Tubular Reabsorption: Useful substances are reabsorbed from the filtrate back into the blood.

3. Tubular Secretion: Additional wastes are secreted from the blood into the tubule for excretion.

Male Reproductive System

Overview and Major Structures

The male reproductive system produces sperm and delivers it to the female reproductive tract. It consists of external and internal organs.

• Penis: Organ for copulation and urination.

  • Corpus Spongiosum: Surrounds the urethra and prevents it from closing during erection.

  • Corpora Cavernosa: Paired erectile bodies that fill with blood during erection.

  • Glans: The expanded tip of the penis.

  • Prepuce: Foreskin covering the glans (if present).

• Scrotum: Sac that holds and regulates the temperature of the testes.

• Testis: Produces sperm and testosterone.

• Epididymis: Site of sperm maturation and storage.

• Spermatic Cord: Contains blood vessels, nerves, and the ductus deferens.

• Ductus (Vas) Deferens: Transports sperm from the epididymis to the ejaculatory duct.

• Ejaculatory Duct: Formed by the union of the ductus deferens and seminal vesicle; passes through the prostate.

• Urethra:

  • Prostatic portion: Passes through the prostate gland.

  • Membranous portion: Passes through the urogenital diaphragm.

  • Penile/Spongy portion: Runs through the penis.

• Seminal Vesicle: Secretes fluid that nourishes sperm.

• Prostate Gland: Adds fluid to semen for sperm motility.

• Bulbourethral Glands: Secrete lubricating mucus.

• Interstitial Cells (Leydig cells): Produce testosterone.

• Sperm Cell:

  • Head: Contains the nucleus and acrosome.

  • Midpiece: Packed with mitochondria for energy.

  • Tail: Flagellum for motility.

Pathway of Sperm from Testis to Exterior

1. Testis

2. Epididymis

3. Ductus (Vas) Deferens

4. Ejaculatory Duct

5. Urethra (prostatic, membranous, penile portions)

Female Reproductive System

Overview and Major Structures

The female reproductive system produces eggs, supports fertilization, and provides an environment for fetal development.

• Ovary: Produces eggs (ova) and hormones.

• Uterine (Fallopian) Tube: Transports egg from ovary to uterus; site of fertilization.

• Fimbriae: Finger-like projections that help guide the egg into the uterine tube.

• Uterus:

  • Fundus: Dome-shaped superior portion.

  • Body: Main part of the uterus.

  • Cervix: Narrow, lower portion opening into the vagina.

• Uterine Wall Layers:

  • Perimetrium: Outer serous layer.

  • Myometrium: Thick muscular layer.

  • Endometrium: Inner mucosal lining; site of implantation.

• Vagina: Muscular canal for intercourse and childbirth.

• Mons Pubis: Fatty area overlying the pubic bone.

• Clitoris: Erectile tissue involved in sexual arousal.

• Labia Majora and Minora: Folds of skin protecting the vaginal opening.

• Breast:

  • Areola: Pigmented area around the nipple.

  • Nipple: Projection through which milk is delivered.

Ovarian Follicle Development

• Primordial Follicle: Immature follicle with a primary oocyte.

• Primary Follicle: Follicle with a single layer of cuboidal cells.

• Secondary Follicle: Follicle with multiple layers of granulosa cells and a developing antrum.

• Tertiary (Graafian) Follicle: Mature follicle with a large antrum, ready for ovulation.

Phases of the Uterine (Menstrual) Cycle

• Proliferative Phase: Endometrium rebuilds after menstruation (estrogen-driven).

• Secretory Phase: Endometrium prepares for implantation (progesterone-driven).

• Menstrual Phase: Shedding of the endometrial lining.

Breast: Resting vs. Active Phases

• Resting Phase: Non-lactating state; ducts and alveoli are small.

• Active Phase: During lactation; alveoli enlarge and produce milk.

Pathway of Egg Cell from Ovary to Exterior

1. Ovary

2. Uterine (Fallopian) Tube

3. Uterus

4. Vagina

Development and Pregnancy

Early Embryonic Development

• Cleavage: Series of rapid mitotic divisions of the zygote.

• Morula: Solid ball of cells resulting from cleavage.

• Blastocyst: Hollow ball of cells with an inner cell mass; implants in the uterus.

• Bilayered Embryonic Disc: Two-layered structure (epiblast and hypoblast).

• Trilayered Embryonic Disc: Three germ layers (ectoderm, mesoderm, endoderm) form via gastrulation.

• Yolk Sac: Early site of blood cell formation.

• Amniotic Cavity: Fluid-filled cavity that cushions the embryo.

Fetal Development (7-Month-Old Fetus Model)

• Fetus: Developing human from 9 weeks to birth.

• Umbilical Cord: Connects fetus to placenta; contains blood vessels for nutrient and waste exchange.

• Placenta: Organ for nutrient, gas, and waste exchange between mother and fetus.

• Uterus: Site of fetal development; includes the cervix (lower opening).

Summary Table: Pathways of Gametes

Summary Table: Uterine Cycle Phases

Additional info: The above notes expand on the listed structures and processes, providing definitions, context, and logical order for pathways and cycles relevant to the urinary, reproductive, and developmental systems.