Urinary system

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🧠 BIOM2020 – Transcript 9 Notes (Kidneys, Bladder, Pelvic Floor)

(Based strictly on the transcript you uploaded)

⭐ Kidney – Key Facts

  • Kidneys receive 20–25% of cardiac output (second only to the brain).

  • Functions mentioned:

    • Vitamin D activation → calcium mobilisation.

    • Blood pressure regulation (RAAS).

    • Continue functioning until 75–80% of function is lost.

    • If one kidney is absent or lost → the other hypertrophies to compensate.

Position & Anatomy

  • Right kidney is lower than the left → due to the liver.

  • Both relate to the 12th rib, left also to the 11th rib.

  • Surrounded by:

    • Renal capsule

    • Adipose tissue

    • Renal fascia
      These fascia anchor kidneys to the respiratory diaphragm.

Internal Structure

  • Two major zones:

    • Cortex (outer, pale)

    • Medulla (inner, darker)

  • Renal pyramids sit in the medulla.

  • Renal columns = cortical tissue between pyramids.

Drainage System

  1. Minor calyces

  2. Major calyces

  3. Renal pelvis

  4. Ureter

Blood Supply

  • Renal artery (branch of abdominal aorta).

Innervation

  • Sympathetic: T12–L1

  • Parasympathetic: Vagus nerve

  • Pain referral: groin + femoral triangle (“hands in pockets”).

⭐ Ureter

  • Muscular tube connecting renal pelvis → bladder.

  • Shares nerve supply with kidney (T12–L1).

  • Pain also refers to groin region.

⭐ Urinary Bladder

  • MUST label as urinary bladder in exams (not just “bladder”).

  • Mean capacity: ~220 mL

    • Desire to void at ~250 mL

    • Pain at ~500 mL

    • Bladder can rupture if struck when full.

Internal Features

  • Rugae (irregular folds) — must specify “of urinary bladder”.

  • Trigone (smooth triangle):

    • 2 ureteric openings

    • 1 urethral opening

Female Relationship

  • Uterus piggybacks on bladder → early pregnancy → frequent urination.

Male Relationship

  • Posterior to bladder:

    • Ductus deferens (“water under the bridge”: ureter = water, ductus = bridge)

    • Seminal vesicles

    • Prostate (enlarges with age → nocturia)

⭐ Urethra

Female

  • Short → higher risk of UTIs.

Male

Four parts:

  1. Pre-prostatic urethra

  2. Prostatic urethra

  3. Membranous urethra (narrowest → catheterisation risk)

  4. Penile urethra

⭐ External Genitalia

Male

  • Scrotum

  • Penis (shaft + glans)

Female

  • Labia majora

  • Labia minora

  • Vestibule (between vagina + labia minora)

Embryology

  • Male scrotum ↔ female labia majora (homologues).

⭐ Pelvic Floor

  • Region bounded by:

    • Ischial tuberosities

    • Pubic symphysis

    • Coccyx

Muscles

  • Levator ani (subdivisions mentioned but not required)

  • Coccygeus

  • Insert into perineal body (central tendon).

Clinical Notes

  • Damage to perineal body (e.g., childbirth) → pelvic organ prolapse.

  • Episiotomy:

    • Midline incision → BAD (damages pelvic floor)

    • Mediolateral preferred.

⭐ Other Key Points from Transcript

  • Largest paranasal sinus = maxillary sinus.

  • Narrowest part of larynx = rima glottidis.

  • Thyroid + cricoid cartilages belong to larynx.

  • Nasal conchae function = air conditioning.

  • Right vs left bronchus differences: size, length, angle.

⭐ End‑of‑Lecture Focus (as stated by lecturer)

You must prioritise:

  1. Kidneys

  2. Bladder

  3. Pelvic floor muscles

And be able to identify on cadaveric specimens:

  • Cortex

  • Medulla

  • Renal pyramids

  • Renal columns