Chapter 12

Question 1

Bones are

Answer 1

Rigid mineralized structure that help perform five major roles in the body

Question 2

The 5 major roles bones help perform in the body

Answer 2

Support
Protection
Movement
Mineral storage
Hematopoiesis

Question 3

Bones are often called ——
There are —— bones in the humans body

Answer 3

• bones are often called Osseous tissue
• 80 axial, 126 appendicular (206)

Question 4

The five shape categories of bones

Answer 4

Long bones
Short bones
Flat bones
Irregular bones
Sesamoid bones

Question 5

Diaphysis

Answer 5

Main shaft-like portion, hollow, cylindrical and thick with compact bone

Question 6

Epiphyses

Answer 6

At distal and proximal ends of the bone that provide points of muscle attachments and stability to joints

Question 7

Articulate cartilage

Answer 7

Thin layer of hyaline cartilage

Question 8

Periosteum

Answer 8

Dense, white fibrous membrane that covers bone (except joint surfaces)

Question 9

Medullary cavity

Answer 9

“Marrow cavity”

Question 10

Endosteum

Answer 10

Thin, fibrous membrane that covers the medullary cavity

Question 11

Compact bone

Answer 11

External table: compact bone around the external (distal) cortex
Internal table: compact bone around the internal (proximal) cortex

Diploe: the region between the external and internal tables, which is composed of cancellous bone

Question 12

Bones differ in?

Answer 12

Both size and shape
They also differ in the amount and proportion of two main types of bone:
Cortical (cortex-> outside) - dense and solid bone, primarily around the edge (outer layer) of bone structures
Cancellous - “spongy born”/ “trabecular bone”
- a network of thin branched crossbeams, which provide structural support of bone structures, primarily found in the center

Question 13

Compact bone constitutes about —— of the total bone mass in adult bones

Answer 13

• compact bone constituents about 80% of total bone mass in adults
• cylinder-shaped structural units “Haversian systems”
• Each osteon surround a Central Canal: delivers nutrient and removes wastes from the metabolically active, but imprisoned, bone cells

Question 14

Structures of the osteon:
Lamellae:

Answer 14

Concentric lamellae: cylinder-shaped layers of calcified matrix in the osteon
Interstitial lamellae: layers of calcified matrix between osteons
Circumferential lamellae: lamellae that run along the inner circumference and outer circumference of a bone

Question 15

Structures of the osteon

Answer 15

Lacunae: smalls spaces in bone matrix that contain tissue fluid and bone cells
Canaliculi: ultra-small canals that radiate in all directions from the lacunae and connect them to teach other and to the central canal
Central Canal: “Osteonal canal”/ “Haversian canal” - lined with endosteum and contains blood vessels,, lymphatic vessels and nerves

Question 16

Bones are held together by and critical for what

Answer 16

Bones are held together by ligaments
Critical structures for support, movements and maintaining homeostasis

Question 17

Bone to bone
Bone to muscle

Answer 17

Bone to bone = ligaments (Sprains)
Bone to muscle - tendons (strains)

Question 18

The three bone cells

Answer 18

Osteoblast:
- “Bone-building” cells -> synthesize and secrete an organic matrix called osteoid
- collagen strands in the osteoid serve as a framework for the formation of hydroxyapatite crystals, which mineralizes the bone tissue
Osteoclast:
- “Bone-destroying” / “Bone-reabsorbing” cells
- Giant multinucleate cells which are responsible for the active erosion of bone minerals (hydrochloric acid (HCL) and collagenase)
Osteocyte:
- “mature cells”
- mature no dividing osteoblasts that have become surrounded by matrix and now lie within Lacunae

Question 19

Cancellous bone consists of?

Answer 19

Cancellous bone consists of about 20% of total bone mass
- They contain no osteons but instead consist of crisscrossing bony branches called trabeculae (“trabecular bone”)

Question 20

Fractal -> cancellous bone

Answer 20

They appear random, but they are more complex in orientation

Question 21

Trabeculae are actually arranged along liens of ——

Answer 21

Arranged along lines of stress
- their size and orientation will there differs between individual bones according to the nature and magnitude of the applied load
- the direction of stresses created by the weight of the body

Question 22

Wolff’s law

Answer 22

• developed from the German Anatomist and surgeon Julius Wolff
• “bone in a healthy person or animal will adapt to the loads under which it is placed”

Question 23

Wolff’s law -> loading

Answer 23

• if loading on a particular bone increases, the bone will removal itself over time to become stronger to resist the sort of loading
• inversely, if the loading on a bone decreases, the bone will become less dense and weaker due to the lack of the stimulus to continued remodeling.
  - osteopenia & osteoporosis

Question 24

Myeloid tissue

Answer 24

Type of soft, diffuse connective tissues, often called bone marrow

Question 25

Two types of myeloid tissue

Answer 25

Red bone marrow: prominent in children and infants -> responsible for the production of red blood cells (RBCs) Yellow bone marrow: prominent in older adults -> is a regular of hematopoietic stem cells being replaced with adipocytes

Question 26

Chondrocyte

Answer 26

- product the tough, rubbery ground substance of cartilage - found in the lacuna ,similar to osteocytes

Question 27

Perichondrium

Answer 27

A connective tissue membrane that surrounds the cartilage mass

Question 28

Hyaline cartilage tissue

Answer 28

- hyalos = glass - the most prevalent type of cartilage - found in support rings of the respiratory tract and covering the ends of bones

Question 29

Fibrocartilage tissue

Answer 29

- strongest and most durable type of cartilage - matrix is rigid and filled with a dense packing of strong white collagen fibers - found in intervertebral disks and in the knee joint (menisci)

Question 30

Elastic cartilage joint

Answer 30

- contains few collagen fibers but large number of very fine elastic fibers - providing flexibility - found in the ear and larynx

Question 31

Articulation:

Answer 31

- a point of contact between the bones “joints” - joints may be classified into three major categories by using either structural of functional schemes

Question 32

Structural

Answer 32

- according to the type of connective tissue - fibrous - cartilaginous - synovial

Question 33

Functional

Answer 33

- according to the degree of movement they permit - synarthroses - amphiarthroses - diathroses

Question 34

Fibrous joints (synarthroses)

Answer 34

- held together by fibrous connective tissue (type and amount will vary based on their articulation) - joints are immovable - the three subtypes: syndesmoses, sutures, gomphoses

Question 35

Amphiarthroses

Answer 35

- joints that are articulated through either hyaline cartilage or fibrocartilage - offer limited movement, in certain circumstances - the two subtypes: synchondroses, symphyses

Question 36

Diarthroses

Answer 36

- the body’s most mobile, numerous and anatomically complex joints (freely movable joints) - the three main groups: uniaxial (hinge and pivot), biaxial (saddle and condyloid), multiracial (ball-and-socket, gliding)

Question 37

Diarthroses -> uniaxial

Answer 37

- synovial joints that permit movement around only one axis and in only one plane - hinge joints: those in which the articulating ends of the boned form a hinge-shaped unit (only back and forth movements); flexion and extension - Pivot joints: those in which a projection of one bone articulates with a ring or notch or another bone

Question 38

Diarthroses -> biaxial

Answer 38

- synovial joints that permit movement around two perpendicular axes in two perpendicular planes - Saddle joint: those in which the articulating ends of the bone resemble reciprocally shaped miniature saddles (allows joints to swing in an arch) - condyloid joints: ellipsoidal joints, those in which a condyle fits into an elliptical socket

Question 39

Diathroses -> multiaxial

Answer 39

- synovial joints that permit movements around three or more axes and in three or more planes - Ball-in-socket joints: a ball-shaped head of one bones fits into a concave depression on another, thereby allowing the first bone to move in many directions - Gliding joints: characterized by relatively flat articulating surfaces that allow limited gliding movements along various axes.

Question 40

Diarthroses seven structures

Answer 40

Joint capsule: sleeve-like extension of the periosteum of each articulating bone Synovial membrane: moist, slippery membrane that lines the inner surface of the joint capsule Articular cartilage: thin layer of hyaline cartilage covering and cushioning the articular surfaces of bones Joint cavity: small space between articulating surfaces of the bones of the joint Menisci (articular disk): pads of fibrocartilage located between the articulating ends of the bones in some Diarthroses Ligament: strong cords of dense, white fibrous tissue Bursae: a closed pillow-like structure, which consists of a synovial membrane filled with synovial fluid

Question 41

Ligaments

Answer 41

Attach bone to bone in a synovial joint (ACL -> anterior cruciate ligament in the knee)

Question 42

Tendons

Answer 42

Attach muscle to bone (Achilles tendon)

Question 43

Both tendons and ligaments are what

Answer 43

Composed of tough connective tissue containing collagen (strong, flexible) - muscles further stabilize joints

Question 44

Osteogenesis

Answer 44

- the forming of new bone

Question 45

Endochondral ossification

Answer 45

- “bone formation in cartilage”

Question 46

Intramembranous ossification

Answer 46

- bones formed within fibrous membrane - occurs within the flat bones

Question 47

Bone development in the embryo

Answer 47

- Early fetal development: cartilage model forms (formed by chondroblasts) - later fetal development: osteoblasts replace cartilage with bone - childhood: primary and secondary ossification sites formed - adolescence: elongation at growth plates

Question 48

Hormone regulation

Answer 48

- preadolescence: growth hormone stimulates bone lengthening - early adolescence: estrogen and testosterone stimulate bone lengthening - late adolescence: estrogen and testosterone cause replacement of cartilage growth plates with bone

Question 49

Intramembranous ossification

Answer 49

- occurs within connective tissue membrane - Osteogenic stem cells -> osteoblasts

Question 50

Ossification centers:

Answer 50

- clusters of differentiated osteoblasts - secreting matrix material and collagenous fibers - bones develop sheets fibrous connective tissue

Question 51

Endochondral ossification

Answer 51

- occurs within cartilage, with bone formation spreading from end to end - cartilage develops periosteum - bones is deposited by osteoblast, which differentiate from stem cells on the inner surface of the periosteum - primary ossification center: develops when blood vessels enter the rapidly changing cartilage model at the midpoint of the diaphysis - secondary ossification center: develops in the epiphysis

Question 52

Bone remodeling

Answer 52

- bone is constantly being broken down and reformed - as much as 18% of bone is recycled each year - this remodeling is regulated by hormones: - parathyroid hormone: - PTH secretion increases when blood levels of Ca++ fall; stimulates osteoclasts to secrete more bone-dissolving enzymes - calcitonin: calcitonin secretion increases when blood levels of Ca++ are high; stimulates osteoblasts to add calcium and phosphate to bone

Question 53

Sprains

Answer 53

- stretched or torn ligaments - heal slowly (few cells and poor blood supply)

Question 54

Bursitis and tendinitis

Answer 54

- inflammation of bursae or tendons

Question 55

Arthritis Osteoporosis

Answer 55

- inflammation of joints - osteoarthritis - rheumatoid arthritis Osteoporosis: excessive bone loss

Question 56

Osteoclasts do what

Answer 56

They break down

Question 57

Osteoblasts do what

Answer 57

Build up