Lecture 2: Histology of the musculoskeletal system (Baekey)

Question 1

Embryonic vs. Fetal periods of growth

Answer 1

embryonic growth = organogenesis, wheras fetal period of growth = growth of existing organs and structures

Question 2

what represents the major component of increase in overall body mass during the fetal growth phase?

Answer 2

growth in the musculoskeletal system

Question 3

ossification/osteogenesis

Answer 3

process of laying down new bone material by osteoblasts

Question 4

when does ossification in long bones begin in humans?

Answer 4

third month of embryonic development

Question 5

when does ossification completely finish in humans?

Answer 5

by 25 yrs

Question 6

epiphysis

Answer 6

end portion of long bone

Question 7

diaphysis

Answer 7

middle portion of long bone

Question 8

In which direction does ossification occur in long bones?

Answer 8

moves outward from diaphysis to epiphysis

Question 9

skull growth in female vs. male baboons

Answer 9

Males continue along the SAME growth trajectory as females, but for a longer period of time

Question 10

4 mechanisms of growth

Answer 10

1) cell proliferation
2) protoplasmic synthesis
3) water uptake
4) intercellular matrix deposition (i.e. connective tissue, cartilage, bone)

Question 11

protoplasmic synthesis

Answer 11

new organic matter is created from nutrient supply via biosynthesis

Question 12

What are ABSOLUTE growth scales used for?

Answer 12

to compare growth within a species

Question 13

What are RELATIVE growth scales used for?

Answer 13

to compare growth between species

Question 14

What is scaling?

Answer 14

The relationship b/w overall body size and the relative sizes of various body parts

Question 15

Geometric vs. elastic scaling

Answer 15

In geometric scaling, all of the proportions stay the same (aka isometry). In elastic scaling, some areas grow disproportionately to others (can be positive or negative allometry)

Question 16

Allometry

Answer 16

a mathematical tool for analyzing scaling. The study of the relationship b/w size and shape.

Question 17

positive allometry

Answer 17

when the body part of interest grows faster than whatever it’s being compared to (i.e. the rest of the body)

Question 18

negative allometry

Answer 18

when the body part of interest grows slower than whatever it’s being compared to (i.e. the rest of the body)

Question 19

growth pattern of the human brain

Answer 19

fetal phase = isometry
early postnatal = negative allometry
late postnatal = little or no growth

Question 20

Major tissue components of the MS system

Answer 20

skeletal muscle, cartilage, bone, connective tissue, associated blood vessels and nerves

Question 21

fetal precursor to skeletal muscle

Answer 21

somite myotomes

Question 22

fetal precursor to connective tissue

Answer 22

somite dermatomes

Question 23

fetal precursor to axial skeleton

Answer 23

somite sclerotomes

Question 24

fetal precursor to appendicular skeleton

Answer 24

lateral plate somatic mesoderm

Question 25

fetal precursor to skull and branchial arch bone + cartilage

Answer 25

head mesenchyme (largely neural crest)

Question 26

fetal precursor to skeletal muscle of head and branchial arches 1-3

Answer 26

somitomeres

Question 27

when do myotome cells become myoblasts?

Answer 27

when they lose the ability to undergo mitosis and begin synthesizing myofibrilar proteins

Question 28

myotube

Answer 28

an elongated multinucleated muscle fibers formed by fused myoblasts. Synthesizes actin and myosin which self-assemble into thick and thin filaments

Question 29

3 main steps of skeletal muscle fiber development

Answer 29

1) mesenchymal cells differentiate into myoblasts. 2) myoblasts fuse to form myotubes. Contractile filaments begin to order peripherally 3) nuclei migrate to periphery and cytoplasm is filled with bundles of contractile filaments in banding pattern

Question 30

3 main layers of muscle

Answer 30

epimysium, perimysium, endomysium

Question 31

epimysium

Answer 31

(fascia) the outer capsule of muscle

Question 32

perimysium

Answer 32

inward extensions of epimysium that package groups of muscle cells into fascicles and bring nerves, blood vessels, and lymphatics into the muscle

Question 33

endomysium

Answer 33

loos connective tissue that surrounds individual multinucleated muscle fibers; brings in capillaries and the smallest division of nerves

Question 34

metaphysis

Answer 34

transition between the epiphysis and diaphysis

Question 35

physes =

Answer 35

growth plates. located at metaphysis. An immovable cartilaginous joint (synchondrosis) b/w the epiphysis and diaphysis

Question 36

characteristics of zone of resting chondrocytes ***

Answer 36

scattered, non-dividing chondrocytes which may serve to weld the growth plate to the epiphysis

Question 37

characteristics of zone of proliferative chondrocytes ***

Answer 37

- isogenic columns of actively dividing chondrocytes - site of elongation of the long bone - more mature chondrocytes located at the diaphyseal end of the columns

Question 38

characteristics of zone of hypertrophied chondrocytes ***

Answer 38

- narrow zone at diaphyseal end of isogenic columns - chondrocytes with lacunae are large and intercellular matrix is minimal - weakest site in the growth plate & major site of fractures

Question 39

chars. of zone of calcified cartilage ***

Answer 39

- calcium deposition appears as dk. stained matrix | - tidemark visible as border b/w zone of articular cartilage and zone of calcification

Question 40

osteoblast fx

Answer 40

deposit successive lamellae of bone matrix along margins of trabeculae

Question 41

osteocyte

Answer 41

an osteoblast that has become trapped inside the deposited matrix. persist as mature bone cells

Question 42

fx of canaliculi

Answer 42

capture blood supply from haversian canal to supply osteocytes within an osteon

Question 43

what does tidemark denote?

Answer 43

the border between articular and mineralized (calcified) cartilage

Question 44

diarthroidal joint

Answer 44

a movable joint

Question 45

synarthroidal joint

Answer 45

an immovable joint

Question 46

synovial joint components

Answer 46

components: articulating bone surfaces covered by hyaline cartilage separated by a fluid-filled joint cavity, surrounded by a joint capsule

Question 47

examples of synovial joint

Answer 47

scapulo-humeral; stifle

Question 48

symphysis joint components

Answer 48

articular surfaces covered by hyaline cartilage, separated by a pad of fibrocartilage

Question 49

examples of symphysis joint

Answer 49

intervertebral, pubic symphysis

Question 50

components of synovial joint capsule

Answer 50

synovial membrane (epithelial-like layer of fibroblasts), synovial fold (infolding of synovial membrane into synovial space), and fibrous layer (dense white fibrous connective tissue that contains elastic fibers)

Question 51

perichondral ring

Answer 51

where fibrous layer of synovial joint capsule attaches to bone. An area of transition b/w the articular cartilage and the periosteum of the diaphysis

Question 52

periosteum

Answer 52

membrane that lines the outer surface of all bones

Question 53

what are tendons composed of?

Answer 53

dense white fibrous connective tissue anchored to bone or muscle

Question 54

Sharpey's fibers

Answer 54

collagenous fibers that attach tendons, ligaments, and joint capsules to bone