PCT Anatomy and Physiology 2 — Questions and Answers
Question 1: Which organ is responsible for filtering blood and producing urine?
- Liver
- Kidney (Correct answer)
- Pancreas
- Spleen
Correct answer: Kidney
The kidneys filter approximately 180 liters of blood daily, removing waste products and excess fluid to produce urine.
The kidneys are bean-shaped organs located behind the peritoneum at the level of T12-L3 vertebrae. Each kidney contains about 1 million nephrons that filter blood, reabsorb needed substances (water, glucose, electrolytes), and excrete waste as urine. The kidneys also regulate blood pressure, electrolyte balance, acid-base balance, and red blood cell production (via erythropoietin).
Question 2: The main function of red blood cells (erythrocytes) is to:
- Fight infection
- Form blood clots
- Transport oxygen to body tissues (Correct answer)
- Produce antibodies
Correct answer: Transport oxygen to body tissues
Red blood cells contain hemoglobin, which binds oxygen in the lungs and delivers it to cells throughout the body.
Erythrocytes are biconcave disc-shaped cells packed with hemoglobin (Hgb), an iron-containing protein that binds oxygen in the pulmonary capillaries and releases it in tissue capillaries. Normal RBC count is 4.5-5.5 million/μL. They also carry carbon dioxide back to the lungs for exhalation. RBCs are produced in bone marrow and live approximately 120 days.
Question 3: The largest organ of the body that serves as a barrier against infection is the:
- Liver
- Brain
- Skin (integumentary system) (Correct answer)
- Small intestine
Correct answer: Skin (integumentary system)
The skin is the largest organ and the body's first line of defense, forming a physical and chemical barrier against pathogens.
The skin (integumentary system) covers approximately 20 square feet in adults and weighs about 8 pounds. It protects against microorganisms (physical barrier, acidic pH, antimicrobial peptides), UV radiation (melanin), dehydration, and temperature extremes. It also contains sensory receptors, produces vitamin D, and helps regulate body temperature through sweating and blood vessel dilation/constriction.
Question 4: Which chamber of the heart pumps oxygenated blood to the body?
- Right atrium
- Right ventricle
- Left atrium
- Left ventricle (Correct answer)
Correct answer: Left ventricle
The left ventricle is the strongest chamber, generating enough pressure to pump oxygenated blood through the aorta to the entire systemic circulation.
Blood flow through the heart: deoxygenated blood enters the right atrium via vena cavae → right ventricle → pulmonary artery → lungs (gas exchange) → pulmonary veins → left atrium → left ventricle → aorta → body. The left ventricle has the thickest walls (3x thicker than right) because it must generate enough pressure to circulate blood through the entire systemic circuit.
Question 5: The exchange of oxygen and carbon dioxide occurs in which structures of the lungs?
- Bronchi
- Trachea
- Alveoli (Correct answer)
- Pleura
Correct answer: Alveoli
Alveoli are tiny air sacs surrounded by capillaries where gas exchange occurs through a thin membrane by diffusion.
The lungs contain approximately 300 million alveoli, providing a surface area of about 70 square meters for gas exchange. Each alveolus is surrounded by pulmonary capillaries. Oxygen diffuses from alveolar air (high concentration) into blood (low concentration), while carbon dioxide diffuses in the opposite direction. The alveolar-capillary membrane is only 0.5 micrometers thick, enabling rapid diffusion.
Question 6: The central nervous system (CNS) consists of:
- The brain and cranial nerves
- The brain and spinal cord (Correct answer)
- The spinal cord and peripheral nerves
- The autonomic and somatic nervous systems
Correct answer: The brain and spinal cord
The CNS comprises the brain and spinal cord, which together process information and coordinate all body functions.
The central nervous system includes the brain (cerebrum, cerebellum, brainstem) and spinal cord. The CNS processes sensory input, integrates information, and generates motor responses. It is protected by bone (cranium and vertebral column), three layers of meninges (dura mater, arachnoid mater, pia mater), and cerebrospinal fluid. The peripheral nervous system (PNS) connects the CNS to the rest of the body via nerves.
PCT Anatomy and Physiology 2
Which organ is responsible for filtering blood and producing urine?