Skeletal System Structure, Mineral Homeostasis (3B) - MCAT Biological and Biochemical Foundations of Living Systems
Card 1 of 25
What structure runs perpendicular to Haversian canals to connect osteons?
What structure runs perpendicular to Haversian canals to connect osteons?
Tap to reveal answer
Volkmann canals (perforating canals). Volkmann canals facilitate nutrient and waste exchange by linking Haversian systems transversely.
Volkmann canals (perforating canals). Volkmann canals facilitate nutrient and waste exchange by linking Haversian systems transversely.
← Didn't Know|Knew It →
What are canaliculi in compact bone?
What are canaliculi in compact bone?
Tap to reveal answer
Channels connecting lacunae for nutrient and signal exchange. Canaliculi enable osteocytes to communicate and exchange nutrients despite being encased in bone.
Channels connecting lacunae for nutrient and signal exchange. Canaliculi enable osteocytes to communicate and exchange nutrients despite being encased in bone.
← Didn't Know|Knew It →
What is the key structural difference between compact and spongy bone?
What is the key structural difference between compact and spongy bone?
Tap to reveal answer
Compact: osteons; spongy: trabeculae with marrow spaces. Compact bone's dense osteons provide strength, while spongy bone's trabeculae offer lightness and marrow space.
Compact: osteons; spongy: trabeculae with marrow spaces. Compact bone's dense osteons provide strength, while spongy bone's trabeculae offer lightness and marrow space.
← Didn't Know|Knew It →
What is the primary inorganic mineral in bone matrix?
What is the primary inorganic mineral in bone matrix?
Tap to reveal answer
Hydroxyapatite (calcium phosphate). Hydroxyapatite crystals provide compressive strength and rigidity to the bone matrix.
Hydroxyapatite (calcium phosphate). Hydroxyapatite crystals provide compressive strength and rigidity to the bone matrix.
← Didn't Know|Knew It →
What are the four major bone cell types and their primary roles?
What are the four major bone cell types and their primary roles?
Tap to reveal answer
Osteoblast build; osteoclast resorb; osteocyte maintain; progenitor form. These cells collaborate in bone formation, resorption, maintenance, and regeneration to ensure skeletal integrity and remodeling.
Osteoblast build; osteoclast resorb; osteocyte maintain; progenitor form. These cells collaborate in bone formation, resorption, maintenance, and regeneration to ensure skeletal integrity and remodeling.
← Didn't Know|Knew It →
What are lacunae in bone tissue?
What are lacunae in bone tissue?
Tap to reveal answer
Small cavities that house osteocytes. Lacunae embed osteocytes within the mineralized matrix, allowing them to sense mechanical stress.
Small cavities that house osteocytes. Lacunae embed osteocytes within the mineralized matrix, allowing them to sense mechanical stress.
← Didn't Know|Knew It →
What is the primary organic component of bone matrix?
What is the primary organic component of bone matrix?
Tap to reveal answer
Type I collagen (osteoid). Type I collagen forms the flexible organic framework that is mineralized to create bone tissue.
Type I collagen (osteoid). Type I collagen forms the flexible organic framework that is mineralized to create bone tissue.
← Didn't Know|Knew It →
What is an osteon (Haversian system) in compact bone?
What is an osteon (Haversian system) in compact bone?
Tap to reveal answer
Concentric lamellae around a central (Haversian) canal. Osteons form the structural units of compact bone, providing strength and housing vascular channels.
Concentric lamellae around a central (Haversian) canal. Osteons form the structural units of compact bone, providing strength and housing vascular channels.
← Didn't Know|Knew It →
What is the functional significance of trabeculae in spongy bone?
What is the functional significance of trabeculae in spongy bone?
Tap to reveal answer
Reduce weight and align along lines of stress. Trabeculae optimize bone's strength-to-weight ratio by aligning with mechanical forces per Wolff's law.
Reduce weight and align along lines of stress. Trabeculae optimize bone's strength-to-weight ratio by aligning with mechanical forces per Wolff's law.
← Didn't Know|Knew It →
What is the periosteum and what is its key function?
What is the periosteum and what is its key function?
Tap to reveal answer
Outer fibrous covering; anchors tendons/ligaments and supports growth/repair. The periosteum nourishes bone via blood vessels and houses progenitor cells for repair and growth.
Outer fibrous covering; anchors tendons/ligaments and supports growth/repair. The periosteum nourishes bone via blood vessels and houses progenitor cells for repair and growth.
← Didn't Know|Knew It →
What is the endosteum and where is it located?
What is the endosteum and where is it located?
Tap to reveal answer
Cellular lining of medullary cavity and trabecular surfaces. The endosteum contains osteoprogenitor cells essential for bone remodeling and repair.
Cellular lining of medullary cavity and trabecular surfaces. The endosteum contains osteoprogenitor cells essential for bone remodeling and repair.
← Didn't Know|Knew It →
What is the medullary cavity and what does it typically contain in adults?
What is the medullary cavity and what does it typically contain in adults?
Tap to reveal answer
Central cavity of long bone; usually yellow (fatty) marrow in adults. The medullary cavity stores adipose tissue, serving as an energy reserve in adult long bones.
Central cavity of long bone; usually yellow (fatty) marrow in adults. The medullary cavity stores adipose tissue, serving as an energy reserve in adult long bones.
← Didn't Know|Knew It →
What is the difference between red marrow and yellow marrow?
What is the difference between red marrow and yellow marrow?
Tap to reveal answer
Red: hematopoiesis; yellow: fat storage (can revert to red if needed). Red marrow produces blood cells, while yellow marrow stores fat but can convert for increased hematopoiesis.
Red: hematopoiesis; yellow: fat storage (can revert to red if needed). Red marrow produces blood cells, while yellow marrow stores fat but can convert for increased hematopoiesis.
← Didn't Know|Knew It →
What are the main functions of the skeletal system tested on the MCAT?
What are the main functions of the skeletal system tested on the MCAT?
Tap to reveal answer
Support, protection, movement, mineral storage, hematopoiesis. The skeletal system provides structural support, protects organs, enables mobility, stores minerals, and produces blood cells.
Support, protection, movement, mineral storage, hematopoiesis. The skeletal system provides structural support, protects organs, enables mobility, stores minerals, and produces blood cells.
← Didn't Know|Knew It →
What is intramembranous ossification and which bones primarily use it?
What is intramembranous ossification and which bones primarily use it?
Tap to reveal answer
Bone forms from mesenchyme; flat bones (skull, clavicle). Intramembranous ossification directly converts mesenchymal tissue to bone, typical for flat bones like the skull.
Bone forms from mesenchyme; flat bones (skull, clavicle). Intramembranous ossification directly converts mesenchymal tissue to bone, typical for flat bones like the skull.
← Didn't Know|Knew It →
What is endochondral ossification and which bones primarily use it?
What is endochondral ossification and which bones primarily use it?
Tap to reveal answer
Bone replaces cartilage model; long bones. Endochondral ossification uses a cartilage template replaced by bone, enabling longitudinal growth in long bones.
Bone replaces cartilage model; long bones. Endochondral ossification uses a cartilage template replaced by bone, enabling longitudinal growth in long bones.
← Didn't Know|Knew It →
What is the epiphyseal (growth) plate and what happens to it after puberty?
What is the epiphyseal (growth) plate and what happens to it after puberty?
Tap to reveal answer
Hyaline cartilage growth zone; closes to epiphyseal line. The epiphyseal plate facilitates bone lengthening through chondrocyte proliferation until fusing post-puberty.
Hyaline cartilage growth zone; closes to epiphyseal line. The epiphyseal plate facilitates bone lengthening through chondrocyte proliferation until fusing post-puberty.
← Didn't Know|Knew It →
What are the two main hormones that directly regulate blood calcium homeostasis?
What are the two main hormones that directly regulate blood calcium homeostasis?
Tap to reveal answer
Parathyroid hormone (PTH) and calcitonin. PTH and calcitonin maintain calcium balance by opposing effects on bone, kidney, and intestine.
Parathyroid hormone (PTH) and calcitonin. PTH and calcitonin maintain calcium balance by opposing effects on bone, kidney, and intestine.
← Didn't Know|Knew It →
Which option best describes the net effect of PTH on serum $\text{Ca}^{2+}$?
Which option best describes the net effect of PTH on serum $\text{Ca}^{2+}$?
Tap to reveal answer
Increases serum $\text{Ca}^{2+}$. PTH elevates blood calcium by promoting bone resorption, renal reabsorption, and vitamin D activation.
Increases serum $\text{Ca}^{2+}$. PTH elevates blood calcium by promoting bone resorption, renal reabsorption, and vitamin D activation.
← Didn't Know|Knew It →
Which option best describes the net effect of calcitonin on serum $\text{Ca}^{2+}$?
Which option best describes the net effect of calcitonin on serum $\text{Ca}^{2+}$?
Tap to reveal answer
Decreases serum $\text{Ca}^{2+}$. Calcitonin lowers blood calcium by inhibiting osteoclast activity and enhancing renal excretion.
Decreases serum $\text{Ca}^{2+}$. Calcitonin lowers blood calcium by inhibiting osteoclast activity and enhancing renal excretion.
← Didn't Know|Knew It →
What is the net renal effect of PTH on phosphate reabsorption?
What is the net renal effect of PTH on phosphate reabsorption?
Tap to reveal answer
Decreases phosphate reabsorption (increases phosphate excretion). PTH promotes phosphaturia to balance calcium mobilization and prevent precipitation in tissues.
Decreases phosphate reabsorption (increases phosphate excretion). PTH promotes phosphaturia to balance calcium mobilization and prevent precipitation in tissues.
← Didn't Know|Knew It →
What is the active form of vitamin D that increases intestinal calcium absorption?
What is the active form of vitamin D that increases intestinal calcium absorption?
Tap to reveal answer
Calcitriol ($1,25$-dihydroxyvitamin D). Calcitriol, activated in the kidney, enhances intestinal uptake of calcium and phosphate for homeostasis.
Calcitriol ($1,25$-dihydroxyvitamin D). Calcitriol, activated in the kidney, enhances intestinal uptake of calcium and phosphate for homeostasis.
← Didn't Know|Knew It →
Identify the bone remodeling cell activated by RANKL signaling from osteoblast lineage cells.
Identify the bone remodeling cell activated by RANKL signaling from osteoblast lineage cells.
Tap to reveal answer
Osteoclast (via RANK activation on osteoclast precursors). RANKL from osteoblasts binds RANK to differentiate precursors into mature osteoclasts for resorption.
Osteoclast (via RANK activation on osteoclast precursors). RANKL from osteoblasts binds RANK to differentiate precursors into mature osteoclasts for resorption.
← Didn't Know|Knew It →
Which option best describes the net effect of mechanical loading on bone mass?
Which option best describes the net effect of mechanical loading on bone mass?
Tap to reveal answer
Increases bone formation and bone density (Wolff law). Mechanical stress stimulates osteoblast activity, leading to bone adaptation and increased density per Wolff's law.
Increases bone formation and bone density (Wolff law). Mechanical stress stimulates osteoblast activity, leading to bone adaptation and increased density per Wolff's law.
← Didn't Know|Knew It →
What is the primary mineral reservoir function of bone in homeostasis?
What is the primary mineral reservoir function of bone in homeostasis?
Tap to reveal answer
Storage and release of $\text{Ca}^{2+}$ and phosphate as needed. Bone acts as a dynamic reservoir, mobilizing minerals via hormonal regulation to maintain blood levels.
Storage and release of $\text{Ca}^{2+}$ and phosphate as needed. Bone acts as a dynamic reservoir, mobilizing minerals via hormonal regulation to maintain blood levels.
← Didn't Know|Knew It →