CTBS Anatomy and Physiology 5 — Questions and Answers
Question 1: In eye banking, the corneal endothelium is critical because it maintains corneal transparency through which mechanism?
- Producing collagen to maintain stromal thickness
- Active ion pumping to prevent stromal swelling (deturgescence) (Correct answer)
- Filtering ultraviolet light before it reaches the lens
- Secreting tear film precursors onto the ocular surface
Correct answer: Active ion pumping to prevent stromal swelling (deturgescence)
The corneal endothelium uses Na+/K+-ATPase pumps to actively remove fluid from the stroma, preventing edema and maintaining optical clarity.
Question 2: The thoracic duct, the largest lymphatic vessel, drains lymph from most of the body and empties into which venous junction?
- Right subclavian-jugular junction
- Left subclavian-jugular junction (left venous angle) (Correct answer)
- Superior vena cava directly
- Inferior vena cava at the hepatic level
Correct answer: Left subclavian-jugular junction (left venous angle)
The thoracic duct ascends through the thorax and empties into the venous system at the left subclavian-internal jugular junction (left venous angle).
Question 3: A tissue bank specialist evaluating donor bone notes osteocytes are found in small spaces called lacunae. How do osteocytes communicate with each other within dense bone?
- Through fenestrations in the Haversian canal walls
- Via cytoplasmic extensions through canaliculi connecting lacunae (Correct answer)
- By secreting hormones into the periosteal blood supply
- Through gap junctions at the bone surface only
Correct answer: Via cytoplasmic extensions through canaliculi connecting lacunae
Osteocytes extend cytoplasmic processes through tiny channels called canaliculi that connect neighboring lacunae, enabling nutrient and signaling molecule exchange.
Question 4: When documenting a musculoskeletal recovery, a specialist notes the iliotibial (IT) band. This structure is a thickening of which fascial layer?
- Fascia lata of the thigh (Correct answer)
- Crural fascia of the leg
- Deep fascia of the gluteus maximus
- Superficial fascia of the lateral hip
Correct answer: Fascia lata of the thigh
The iliotibial band is a lateral thickening of the fascia lata, the deep fascia enveloping the thigh, running from the iliac crest to Gerdy's tubercle on the tibia.
Question 5: In the context of amniotic membrane tissue banking, the amnion is derived from which embryonic germ layer?
- Mesoderm only
- Ectoderm only
- Both ectoderm (epithelium) and mesoderm (stromal layer) (Correct answer)
- Endoderm and mesoderm
Correct answer: Both ectoderm (epithelium) and mesoderm (stromal layer)
The amniotic membrane has an epithelial layer derived from ectoderm and a stromal/mesenchymal layer derived from mesoderm, making it a bilaminar structure.
Question 6: Which anatomical region of the femur is most commonly used as a source of cortical bone struts in structural allograft procedures?
- Femoral head
- Femoral neck
- Femoral shaft (diaphysis) (Correct answer)
- Medial femoral condyle
Correct answer: Femoral shaft (diaphysis)
The femoral shaft (diaphysis) provides long segments of dense cortical bone ideal for structural strut allografts in spinal and long-bone reconstruction.
Question 7: The lymphatic vessels in tissue act as a secondary circulatory system. Which statement correctly describes the direction of lymph flow?
- From lymph nodes toward the tissues and back to the heart
- From the interstitial tissue spaces toward the thoracic duct and into venous circulation (Correct answer)
- Bidirectional, driven by lymphatic valves that allow flow in both directions
- From the thoracic duct outward to peripheral tissues carrying nutrients
Correct answer: From the interstitial tissue spaces toward the thoracic duct and into venous circulation
Lymph flows unidirectionally from interstitial spaces through capillaries and vessels, through lymph nodes, and ultimately into venous blood via the thoracic duct.
CTBS Anatomy and Physiology 5
In eye banking, the corneal endothelium is critical because it maintains corneal transparency through which mechanism?