Exam 2 Ch. 6 Study Guide Questions Flashcards
Define and also identify visually the macroscopic structure of bone including diaphysis, epiphysis, metaphysis, medullary cavity, periosteum, endosteum, and articular cartilage.
•Diaphysis - shaft of long bone
•Epiphysis - ends of long bone
•Metaphysis - between epiphysis and diaphysis usually referring to epiphyseal growth plate
•Medullary cavity - space inside diaphysis containing marrow
•Periosteum - connective tissue covering bone
•Endosteum - connective tissues lining medullary cavity
•Articular cartilage - surface of epiphyses where bones meet (joints)
Which type of cartilage is articular cartilage? Where is it found?
Hyaline cartilage (chondrocytes in lacunae surrounded by matrix of dense collagen fibers)
Found in epiphyses, end of nose, connection between ribs and sternum, epiphyseal growth plate
Which form of marrow stores fats in adults?
Yellow marrow
What houses osteocytes?
Lacunae
Which two routes provide osteon’s their blood supplies?
Central/Haversian/Osteonic canals and Volkmann’s/ perforating canals
Through what structures do bone cells “talk”?
Canaliculi
How does spongy and compact bone differ structurally?
•Spongy - unit = trabeculae “swiss cheese,”spaces filled with marrow, best for compression
•Compact - unit = osteon in layered cylinder (like tree/tree rings), blood vessels via canals, best for
bending
Name and define the cells and osteoid of compact bone. Which cells produce matrix? Which are “bone breakers”? Why is it important in remodeling?
•Osteocytes - mature bone cells, maintenance in lacunae
•Osteoblasts - build organic matrix (osteoid is collagen and proteoglycans)
•Osteoclasts - “bone breakers” resorb (remove) bone material
•Respectively osteoclasts and osteoblasts breakdown and rebuilt bone continuously in remodeling.
What is the major component of hydroxyapatite? What does it contribute to bone?
Calcium phosphate; contributes hardness
Name four general functions of bone.
Support, protection, movement, storage, blood cell production
In what bones do you see intramembranous ossification?
Skull bones, mandible, clavicle
Describe the process of intramembranous and endochondral ossification. Which cells start the ossification process in both cases? What are the main non-bone starting tissues in each?
•Intramembranous ossification - center of ossification starts with fibrous connective tissue membrane (non-bone starting tissue aka mesenchyme) ➡️ osteoprogenitor cells ➡️ osteoblasts which build bone matrix form and increase trabeculae size to form spongy bone ➡️ osteocytes maintain bone within lacunae ➡️ surface layers are converted to compact bone while fibrous connective tissue remains as periosteum
•Endochondral ossification - primary center of ossification starts in the middle of diaphysis and the hyaline cartilage (non-bone starting tissue) ➡️ osteoblasts secrete matrix to create spongy bone which continues to replace hyaline migrating towards ends of diaphysis ➡️ hyaline cartilage dissolves as calcification takes place ➡️ spongy bone is converted to compact bone and medullary cavity ➡️ secondary center of ossification occurs in epiphyses mostly after birth ➡️ same process except remains spongy ➡️ hyaline cartilage remains as articular cartilage and epiphyseal growth plate
Where is the primary center of ossification? How does the medullary cavity form afterwards?
Middle of diaphysis
Medullary cavity carved out be osteoclasts.
Where is hyaline cartilage located in a long bone after secondary ossification?
Articular cartilage of epiphyses and epiphyseal growth plate
How do bones lengthen? What is the spacing relationship between chondrocytes and osteoblasts? What closes to stop lengthening? Why?
Interstitial growth (lengthening) is due to the hyaline cartilage epiphyseal growth plate and chondrocytes remaining active in mitosis. Osteoblasts “chase” the cartilage and replace with bone matrix and calcification. As long as hyaline still present, lengthening continues. Once hyaline has been “caught” by ossification, the epiphyseal growth plate is “closed” and lengthening stops.
What are the roles of osteoblasts and osteoclasts in appositional growth?
To widen bone (appositional) proportionally to lengthening (interstitial), osteoblasts build matrix on surface of diaphysis while osteoclasts remove/resorb bone interiorly within the medullary cavity.
Name two hormones which play a role in bone growth.
growth hormone, thyroid hormone, estrogen, testosterone
Define the PTH and calcitonin hormonal control of calcium. Using the negative feedback model, give their site of formation, stimulus and effect in increasing or decreasing blood Ca concentrations.
•Chemoreceptors pick up stimulus of low blood calcium (normal range 9-11 mg/dI) ➡️ activates parathyroid gland (control center) to secrete parathyroid hormone ➡️ PTH travels through bloodstream to cause 1) osteoclasts (effector) to resorb/remove Ca from bone and place in blood (effect), 2) increase kidney Ca reabsorption from blood to reduce Ca excretion in urine, 3) increase calcitriol (activated vitamin D3) which stimulates increase in Ca absorption in Gl tract ➡️ all these increase blood Ca
•Mostly high blood Ca would reduce the PTH activity but if very high, chemoreceptors activate C cells (parafollicular cells of thyroid) to secrete calcitonin - travels through bloodstream to mostly decrease osteoclast activity to keep Ca in bone thus reducing blood Ca.
Which fracture is actually an incomplete break? What is a comminuted fracture?
Greenstick
Comminuted - fragmented
What happens after hematoma formation in the bone repair process? Which type of bone is the bony callus?
•The next step after hematoma is the soft (fibrocartilaginous) callus formation which stabilizes the broken area and becomes template for hard (bony or osseous) callus formation.
•Spongy first, then remodeled into compact.
Why do menopause and smoking contribute to osteoporosis? How does Boniva (or equivalents) generally work?
•Reduce estrogen levels in females. Estrogen is the “brake” for PTH. Without that brake PTH stimulates too much bone removal/resorption from bone.
•Boniva style medications inhibit/kill osteoclasts to reduce bone removal
How does Vitamin D help as a treatment for osteomalacia and rickets?
Activated Vitamin D improves Gl absorption of calcium which strengthens/hardens bones.
