Gross and Microscopic Anatomy of the Bone Flashcards
1
Q
Skeletal Cartilage
A
- primary water, does not contain nerves or blood vessels
- surrounded by a layer of dense irregular tissue: the perichondrium
- basic components: chondrocytes and extracellular matrix
- 3 types (hyaline, elastic, fibrocartilage
2
Q
Hyaline
A
- most abundant
- provides support, flexibility, resistance
- contains spherical chondrocytes + collagen fibers
- ex: articular (joint) surfaces, costal (ribs), larynx, trachea, nose
3
Q
Elastic
A
similar to hyaline but w more elastic fibers
- ex: external ear, epiglottis
4
Q
Fibrocartilage
A
- contains thick collagen fibers
- highly compressible, great tensile strength
- ex: menisci of the knee, intervertebral discs
5
Q
Chondrocytes
A
cartilage forming cells
6
Q
Cartilage growth
A
2 main types:
- appositional
- interstitial
Calcification (hardening) of the cartilage occurs during normal bone growth. it can also occur in older age
- calcified cartilage is NOT the same as bone
7
Q
Appositional growth
A
chondrocytes in the perichondrium secrete matrix against the external face of existing cartilage
8
Q
Interstitial growth
A
chondrocytes within lacunae divide and secrete new matrix - cartilage grows from within
9
Q
Support
A
for body and soft organs
10
Q
Protection
A
protect brain, spinal cord, and vital organs
11
Q
Movement
A
provide levers for muscle action
12
Q
Mineral + growth factor storage
A
calcium + phosphorus + growth factor are stored / released as needed
13
Q
Hematopoiesis
A
(blood cell formation) occurs within red bone marrow
14
Q
Triglyceride / fat storage
A
yellow marrow in some bone cavities
15
Q
Hormone production
A
osteocalcin is secreted by bones to help regulate glucose levels / insulin secretion
16
Q
Classification of Bone
A
- 206 bones total
- individual bone shape is determined by function
- axial vs appendicular skeleton
17
Q
Bone Structure
A
because bones are organs, they contain multiple types of tissue:
- osseous connective tissue (most abundant)
- cartilage
- dense connective tissue
- nervous tissue
- muscle tissue
- epithelial tissue
18
Q
Anatomy of bones
A
- compact bone sandwiching spongy bone
- open spaces between trabeculae are filled with red or yellow bone marrow
19
Q
Spongy bone (trabecular bone)
A
a honeycomb of small, needle-like, or flat pieces of bone called trabeculae (“little beams”)
20
Q
Gross anatomy: short, irregular, and flat bones
A
- contain thin plates of spongy bone (diploe) sandwiched between compact bone
- compact bone is sandwiched between connective tissue membranes (periosteum & endosteum)
- bone marrow is scattered throughout the trabeculae - no defined marrow cavity
- hylaine cartilage covers the areas involved in movable joints
21
Q
Periosteum
A
covers the outside of compact bone
22
Q
Endosteum
A
covers the inside of compact bone
23
Q
Gross anatomy: typical long bone
A
- Diaphysis: tubular shaft, forms the long bone’s long axis
- Epiphyses: ends of long bone
- Epiphyseal line: between diaphysis and epiphyses, remnant of epiphyseal (growth plate) - where bone growth occurred
24
Q
Diaphysis
A
- thick collar of compact bone surrounding a central medullary cavity - filled with yellow marrow
- there is often a thin layer of spongy bone between the compact bone and the cavity
25
Epiphyses
- consists of compact bone externally and spongy bone internally
- the ends of a long bone are covered in hyaline cartilage
26
Periosteum
white, double layered membrane; covers all external surfaces except for joint surfaces; acts as anchoring point for tendons / ligaments
- fibrous layer: outer layer made of dense irregular tissue; secured to bone matrix by perforating fibers
- osteogenic layer: inner layer abutting bone; contains osteogenic stems calls that give rise to most bone cells
27
Endosteum
delicate connective tissue membrane covering the internal bone surface
- covers the trabeculae of spongy bone
- line the canals that pass through compact bone
- also contains osteogenic cells with the ability to differentiate into other bone cells
28
Blood vessels and nerves
- bones are well vascularized
- nutrient arteries and veins run through a hole in the wall of the diaphysis, the nutrient forament
- nutrient arteries supply the spongy bone and bone marrow; branches extend outward to supply the compact bone
- epiphyseal arteries and veins similarly supply the epiphysis
29
Hematopoietic tissue
Red marrow: hematopoietic (blood-forming) tissue
- in newborns, medullary cavities and all spongy bone contain red marrow
- in adults, red marrow exists in the heads of the femur and the humerus, the flat bones, and the irregular bones
- most active areas of hematopoiesis are the diploe of the flat bones and some irregular bones
- yellow marrow can convert to red marrow in the setting of severe anemia
30
Bone markings
- sites of muscle, ligament, and tendon attachment on the external surfaces of bones
- sites involved in joint formation
- conduits for blood vessels and nerves
3 major types:
- projections
- depressions
- openings
31
Projection
outward bulge of bone; may result from increased stress from muscle pull or as a modification for joints
32
Depression
bowl or groove-like cut out; can serve as a passageway for vessels or nerves; plays a role in joints
33
Opening
hole or canal in bone; serves as passageway for blood vessels or nerves
34
Cells of bone tissue
5 major types:
- osteoprogenitor cells
- osteoblasts
- osteocytes
- bone-lining cells
- osteoclasts
the presence of cells is what makes a bone a dynamic living tissue w the ability to remodel
35
Osteoprogenitor cells (osteogenic cells)
- mitotically active stem cells in the periosteum and endosteum
- can differentiate into osteoblasts when stimulated
- others will remain osteogenic cells
36
Osteoblasts
- mitotically active bone-forming cells; secrete unmineralized bone matrix called osteoid
- osteoid is made of collagen and calcium-binding proteins
- when osteoblasts become surrounded by the matrix being secreted, the become osteocytes
37
Osteocytes
- spider-like in appearance
- mature bone cells in lacunae, no longer actively dividing
- maintain bone matrix; act as stress/strain receptors
- respond to mechanical stimuli + changing calcium levels by communicating to osteoblasts / osteoclasts
38
Bone-lining cells
- flat cells on bone surfaces, believed to jekp maintain matrix (w osteocytes)
- called periosteal cells on the external bone surface and endosteal cells on the internal bone surface
39
Osteoclasts
- derived from the same hematopoietic stem cells that become macrophages
- giant, multinucleate cells that function in bone resorption (breakdown)
- ruffed edges to increase surface area
- when active, located in depressions called resortption bays
40
Microscopic anatomy of the bone
Compact bone
- osteon (haverian system)
- canals and canaliciuli
- interstitial and circumferential lamellae
Spongy bone
41
Osteon (haverian system)
- the stuctural unit of compact bone
- elongated cylinders running parallel to the long axis of the bone - act as weight-bearing pillars
- each cylinder consists of rings of bone matrix called lamellae
- each lamella contains collagen fibers-fibers run in different directions in adjacent rings
- cone salts are found between collagen fibers - also alternate their directions between lamellae
42
Central (haversian) canal
runs through the core of the osteon - contains blood vessels and nerves
43
Perforating (volkmann's) canals
canals lined with endosteum, occur at right angles to the central canal - connect blood vessels and nerves of the periosteum, medullary cavity, and central canal
44
Lacunae
small cavities containing osteocytes, occur at the junctions of the lamellae
45
Canaliculi
hairlike canals that connect lacunae to each other and to the central canal
46
Formation of canaliculi
- as osteoblasts secrete bone matrix, they become trapped within and become osteocytes
- tentacles of spidery osteocytes maintain their connections w each other as bone hardens
- a network of tiny canals containing the osteocyte extensions is created
- canaliculi tie all the osteocytes in a mature osteon together and allow communication + passage of nutrients & waste
47
Interstitial lamellae
- incomplete lamellae that lie between complete osteons
- either fill the gaps between forming osteons or are remnants of osteons cut by bone remodeling
48
Circumferential lamellae
- deep to the periosteum but superficial to the endosteum, extend around the entire surface of the diaphysis
- resist the long bone twisting
49
Spongy bone anatomy
- appears poorly organized, but isn't
- trabeculae are organized along the lines of stress
- no osteons are present
- irregularly arranged lamellae and osteocytes interconnected by canaliculi are present
- supplied with nutrients by the capillaries in the endosteum
50
Chemical composition of bone
Organic components
- bone cells and osteoid (ground substance + collagen fibers)
- present to resist tension / stretch
Inorganic Components
- Hydroxyapatites (mineral salts)
- make up 65% of bone by mass
- mainly tiny calcium phosphate crystals
- present to create hardness and resist compression
