HISTOLOGY - Bone & Cartilage Flashcards

Question

What are the 4 bone cell types and what are their functions and roles?

Answer 1

**Osteoprogenitors/osteogenic cells** -from mesenchymal cells that *produce osteoblasts* **Osteoblasts** -*Initiate and control* the mineralization of osteoid via secretion of **_osteoid_** **Osteocytes** - mature bone cells housed in lacunae that *maintain bone matrix* - Has spider-like processes that extend through multiple layers of bone **Osteoclasts** -Multinucelated cell from monocytes that reabsorbs bone (breaks it down) using its "ruffled border" which secretes H+ and lysosomal proteins (ACID)

Answer 2

compact and cancellous

Answer 3

**Compact (cortical) ---- covered by periosteum** 1) lamellar bone (mature) 2) solid, dense 3) nexternal surfaces of long and flat bones **Cancellous (spongy)** 1) lamellar (mature) or woven (immature) bone 2) **Trabecular** bone --- open lattice of narrow plates 3) Internal layer of bone **Compact encloses Cancellous --- MOST BONES HAVE BOTH**

Answer 4

- Immature/primary bone -- will grow into lamellar (mature) bone (**ALL BONE WILL START AS WOVEN**) - Characterized by loose arrangement of collagen fibers - Low mineral content - **Forms during fracture repair and remodling**

Answer 5

The jaw - why we can make teeth move around

Answer 6

**Epiphysis** - knobby region at ends of bone - **contains epiphyseal plate** **Diaphysis** - shaft/body of the bone **Metaphysis** - area between diaphysis and epiphysis (has spongy bone) **Epiphyseal Line** --- remnant of the growth plate we had as kids (fused epiphyseal plate) **Marrow Cavity** -- cylindrical space in diaphysis containing bone marrow

Answer 7

**Periosteum** 1) Comprised of Dense Irregular CT (**important because tendons and ligaments need to attached)** 2) Surround long bones 3) Anchored by **perforating fibers** and contain **osteoblasts** **4) HELPS BONE HAVE FLEXIBILITY** **Endosteum** 1) CT 2) Lining of all trabeculae (lattice of narrow plates in spongy bone) and marrow cavity 3) Contains **osteoprogenitor cells**, **reticular cells of bone marrow** and **CT fibers**

Answer 8

Cylindrical, latered structures that comprise mature bone (betwen the periosteum and spongy bone)

Answer 9

1) runs parallel to the diasphysis and the entire length of the bone 2) Consists of concentric lamellae that have a **central canal** at the center that **contain neurovasculature** 3) **Perforating canals** that run parallel to the concentric lamellae, connect central canals together so that **if one goes down, the neurovascularture can anastomose with another.** Also they allow vasculature to **connect with the periosteum (outer surface) and endosteum** **(inner surface)** portions of the bone

Answer 10

**Interstitial Lamellae** - "Half pieces" of osteons with two functions: 1) Fill in gaps - helps maintain strength 2) Left over from bone remodling **Circumferential Lamellae** -Line the _INNER_ (lines marrow cavity) and _OUTER_ (lines shaft of bone, under periosteum) circumference of the diaphysis

Answer 11

- Osteoclasts - Interact via **Canaliculi** - **tiny channels between Lacunae**

Answer 12

Bone starts as unwoven and then overtime, as the bone grows, osteons form over interstitial lamellae. Overtime, octeoclasts break down (partially) the osteons and new ones are created, staking them on top of one another which will eventually create greater bone strength

Answer 13

1) Skull bones 2) bone marrow 3) orientated in a way that **maximizes strength and minimizes mass**

Answer 14

Endochondral and Intramembranous NOTE: Osteogenesis **IS NOT** minerilization **_WOVEN BONE is produced first in both and then replaced by Lamellar Bone_**

Answer 15

- Prexisting "model" hyaline cartilage invaded by osteoblasts, osteoid is secreted and bone begins being made - Bones of the extremities, pectoral and pelvic girdles, pelvis, vertebrae, end of the clavicle

Answer 16

- Bone growth directly from mesenchyme precursors -- osteoblasts diferentiate directly from mesenchyme and begin secreting osteoid - Flat bones of the skull, most facial bones, central part of the clavicle

Answer 17

1) Mesenchymal cells aggregate and begin dividing 2) After sufficient replication, the cells differentiate and bercome **osteoblasts** 3) Osteoid is then released by the osteoblasts 4) Osteoid is calcified, creating a calcified bone matrix ("Islands" form) 5) Osteoblasts within the newly calcified bone matrix become osteocytes and house themselves in LACUNAE (These "islands" are know as **Primary Ossification Centers)** 6) Overtime, the primary ossification centers grow size and eventually connect with one another creating a continuous stretch of bone tissue 7) Trabeculae established first and then compact bone gets layered on top of the outer boundaries

Answer 18

1) Fetal hyaline cartilage develops. The center than extpands and begins to die off, recruiting blood vessels to area 2) Cartilage then calcifies and a bone collor forms around the diaphysis after osteblasts come in since vasculature can now supply them. 3) **Primary ossification center** forms in the dyaphysis (center of bone) 4) Because the epiphyses (ends of bone) need to ossify, cartilage at the ends increase in size and dies off, blood vessels come in and then osteoblasts come in, forming **secondary ossification centers** 5) Bone replaces cartilage in all places EXCEPT in the areas of **articular cartilage** (outmost part of epiphyses) and the **epiphyseal plates**

Answer 19

So it can be manipulated to grow over time -- if it ossified, the size of our bones would remains constant from birth. Once we aredone growing, the epiphyseal plate ossifies, creating the **epiphyseal line**

Answer 20

A) Zone of ossification B) Zone of calcified cartilage C) zone of hypertrophy D) Zone of proliferation E) Zone of reserve cartilage

Answer 21

1) **No active matrix production** (closest to epiphysis/articular cartilage) 2) Area where **cartilage cells are actively producing collagen** (type II & XI) matrix proteins 3) where **cartilage cells are increasing in size** and recruiting vascular invasion via secretory factors 4) Hypertrophied cells begin to degenerate and the **cartilage matrix becomes calcified** 5) Connected with diaphysis and marrow cavity --- area where bone is established sicne blood vessels and osteoprogenitors invade, differentiating into osteoblasts **_KEY!!!! --- Diaphysis will grow/get longer, pushing epiphysis away_**

Answer 22

May cease all future growth of bone!

Answer 23

-Autosomal dominant mutation in Fibroblast growth factor (**FGFR3**) Clinical manifestations: 1) **Dwarfism** (most common reason) 2) Small midface 3) Shortening of long bones 4) Altered spinal curvature

Answer 24

Growth in the circumference of the long bones via osteoblasts in the periosteum (like adding rings to a tree) **-Allows our bones to increase in volume to support our increasing bodyweight overtime** -Begins with formation of bone collar on cartilagenous diaphysis, accompanied by ENLARGEMENT of the marrow cavity **by osteoclasts in endosteum**

Answer 25

Osteoporosis!!

Answer 26

- Can lead to ricketts, where the bone matrix does not calcify normally, causing the epiphyseal plate to bocome distorted by the weight of the body and muscular activity - Bones also grow more slowly and deformed due to the negative impact of the ossification process. Deficiency commonly due to 1) insifficient calcium in diet or 2) failure to produce vitamin D, which is important fdor absorption of Ca2+ by the small interstine

Answer 27

**Deficient calcification of recently formed bone & partial decalcification of already calcified matrix** Causes: 1) Dietary vitamin D deficiency 2) Lack of sun exposure (low vit D) 3) Gastrointestinal disease Can be asymptomatic

Answer 28

**Description**: Bone matrix does not calcify normally **Symptoms** 1) Epiphysealplate can become distorted by normal strains of body weight & muscular activity 2) Bones to grow more slowly and often become deformed 3) Bowlegged, soft skull bones (Craniotabes) **Cause**: -Vitamin D deficiency, decreased absorption of calcium & phosphorus from bowels

Answer 29

- Decrease in bone mass & increased fragility - Loses ability to produce organic matrix (mainly collagen) - Loses Ca2+ & other bone salts * Commonly occurs in the elderly & postmenopausal females * No clinical manifestations until there is a fracture

Answer 30

Degenerative joint disease with causes unknown but it is **related to aging and injury of articular cartilage** **Symptoms** - Chronic joint pain - Various degrees of joint deformity (heberden's nodes, Bouchards nodes) - Affect DIP and PIP and weight bearing joints **Early Stage** Superficial layer of articulkar cartilage is disrupted **Late Stage** destruction of cartilage extends to the bone, where the bone now articulates at joint (**reduced mobility and pain**)

Answer 31

1) Old osteons are reabsorbned by osteoclasts, which create pores/tunnels in the bone 2) Osteoprogenitors go into the tunnels, create osteoblasts who then secrete osteoid to form new bone 3) New osteon forms, trapping osteocysts within its concentric lamellae and overlayer old fragments of osteons while interstitial lamallae remain **5-10% turn over per year in healthy adults**

Answer 32

1) Blood vessels that were injured during the fracture release blood, which clots and forms a hematoma 2) Hematoma is removed and replaced by a fibrocartilage-like mass known as a **_soft callus_** 3) The callus is invaded by 1) blood vessels and 2) osteoblasts, both of which gradually replaced the fibrocartilage with bone woven bone, forming a **hard callus** 4) Woven bone remodled as compact bone and vasculature is restablished

Answer 33

1) Articular cartilage - HYALINE 2) Joint Cavity - space in which fluid resides 3) Articular capsule - Two Layers: Dense Fibrous CT (outside) amnd Loose Synovial (Inside) ---- creates seal withkn joint for fluid 4) Synovial fluid - lubricates joint 5) Reinforcing ligmaments - extra support 6) Nerves and Blood Vessels

Answer 34

1) Lines joint cavity from inside 2) Lubricates cartilage 3) Because it is a vascular membrane, it procvides nutrients to joint 4) PRODUCES SYNOVIAL FLUID 5) Absorbs shock

Answer 35

1) Reduces friction 2) Avascular 3) Comprised of Hyaline cartilage (NO PERIXCHONDRIUM - present in areas where cartilage is not part of a joint) **4) Nourished by synovial fluid**

Answer 36

Synovial joint ## Footnote SM - synovial membrane A - articular cartilage E - epiphyseal growth plate C - articular capsule

Answer 37

- Cartilage present in joints at the ends of bone **on the surfaces of movable joints** - Made of hyaline cartilage (**remnant of original hyaline template used by developing bone)** - Four zones: Superficial, Intermediate, Deep, Calcified

Answer 38

**SZ - Superficial Zone** Contains elongated and flattened chondrocytes **IZ - Intermediate Zone** Contains round chondrocytes **DZ - Deep Zone** Chondrocyes are arranged in short columns **CZ - Calcified Zone** Where the chondrocytes are small and border the subchondral bone (dark stain)

HISTOLOGY - Bone & Cartilage Flashcards

(65 cards)