Unit 3: Respiratory & Urinary Systems

February 20, 2026

Semester 2
BP201T

Introduction to Respiratory & Urinary Systems

Unit 3 covers two vital systems responsible for gas exchange and waste elimination. The Respiratory System section explains how we breathe and transport Oxygen/CO2. The Urinary System section details how the Kidneys filter blood to form urine, regulating fluid balance and blood pressure (RAS mechanism).

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Syllabus & Topics

  • 1Respiratory system: Anatomy of lungs, mechanism of respiration.
  • 2Regulation of respiration.
  • 3Lung Volumes and capacities.
  • 4Transport of respiratory gases.
  • 5Artificial respiration and resuscitation methods.
  • 6Urinary system: Anatomy of kidney and nephrons.
  • 7Functions of kidney and urinary tract.
  • 8Physiology of urine formation.
  • 9Micturition reflex and role of kidneys in acid base balance.
  • 10Role of RAS in kidney and disorders of kidney.

Learning Objectives

Draw the Nephron: Label the parts of a nephron and describe the function of each segment.
Explain Urine Formation: Describe Glomerular Filtration, Tubular Reabsorption, and Secretion.
Define Lung Volumes: Define Tidal Volume, Vital Capacity, and Residual Volume.
Understand RAS: Explain the Renin-Angiotensin-Aldosterone System and its role in BP regulation.
Mechanism of Breathing: Explain the role of the diaphragm and intercostal muscles in inspiration/expiration.

Frequently Asked Questions (FAQs)

Q1. What is the functional unit of the Kidney?

The nephron is the structural and functional unit of the kidney. It is responsible for filtering blood and forming urine.

Q2. What is Vital Capacity?

Vital capacity is the maximum volume of air that a person can forcibly exhale after taking a maximum inhalation.

Q3. Why is the RAS pathway important?

The Renin–Angiotensin System (RAS) is a key long-term mechanism for regulating blood pressure and fluid balance. It is an important target for many antihypertensive drugs.

Q4. What is Glomerular Filtration Rate (GFR)?

Glomerular Filtration Rate (GFR) is the volume of fluid filtered from the renal glomerular capillaries into Bowman’s capsule per unit time. The normal GFR is approximately 125 mL/min in healthy adults.

Q5. How are O₂ and CO₂ transported in blood?

  • Oxygen (O₂) is mainly transported bound to hemoglobin as oxyhemoglobin.

  • Carbon dioxide (CO₂) is transported primarily as bicarbonate ions (HCO₃⁻), and also as carbaminohemoglobin and dissolved in plasma.