Week 2: Skeletal System

Question 1

What are skeletal structures?

Answer 1

• The axial skeleton: Portion of the skeleton located along the midline of the body
  
  • The appendicular skeleton: All other bones of the skeleton (names such because they are appendages of the axial skeleton)
  • Upper and lower limbs (includes girdles)
  • Pectoral and pelvic girdles
  • Arm, forearm and hand
    Thigh, leg and foot

Question 2

Landmark that forms joint: Condyle

Answer 2

Large rounded knobs at the end of a bone that forms articulations with other bones e.g. lateral condyle of the femur

Question 3

Landmark that forms joints: Facet

Answer 3

Smooth, flat (maybe slightly concave or convex) articular surface e.g. Superior articular facet of the vertebra

Question 4

Landmark that forms joints: Head

Answer 4

Usually rounded articular surface supported on the neck. The epiphysis of a long bone e.g. head of the humerus

Question 5

Landmarks for connective tissue attachment points: Crests

Answer 5

Prominent raised edged of bone or elongated projections e.g. iliac crest of the hip

Question 6

Landmarks for connective tissue attachment points: Epicondyle

Answer 6

a roughened projection that sits above a condyle e.g. lateral epicondyle of the femur

Question 7

Landmarks for connective tissue attachment points: Line (linea)

Answer 7

A long narrow ridge or border (less prominent than a crest) e.g. linea aspera of femur

Question 8

Landmarks for connective tissue attachment points: Process

Answer 8

A bulging bony outgrowth of a larger bone e.g. mastoid process of the temporal bone

Question 9

Landmarks for connective tissue attachment points: Protuberance

Answer 9

Similar to processes, they are either a swelling, bulging or protruding part of a bone e.g. mental protuberance of the mandible

Question 10

Landmarks for connective tissue attachment points: Spinous process

Answer 10

A sharp slender projection e.g. spinous process of the vertebra

Question 11

Landmarks for connective tissue attachment points: Trochanter

Answer 11

A very large irregularly shaped projection e.g. only present on the femur e.g. greater and lesser trochanters

Question 12

Landmarks for connective tissue attachment points: Tubercle

Answer 12

Variably sized, rounded projections e.g. grater tubercle of the humerus

Question 13

Landmarks for connective tissue attachment points: Tuberosity

Answer 13

Similar to tubercle but often with a rough surface e.g. maxillary tuberosity

Question 14

Openings/depressions allowing passage of soft tissue or formation of joints: Fissure

Answer 14

A narrow slit between adjacent parts of bones e.g. superior orbital fissure of the sphenoid bone

Question 15

Openings/depressions allowing passage of soft tissue or formation of joints: Foramen

Answer 15

An opening or hole in the bone e.g. mental foramen of the mandible

Question 16

Openings/depressions allowing passage of soft tissue or formation of joints: Fossa

Answer 16

A broad and shallow depression in the bone e.g. temporal fossa

Question 17

Openings/depressions allowing passage of soft tissue or formation of joints: Meatus

Answer 17

A tubelike channel extending into the bone e.g. external auditory meatus of the temporal bone (ear canal)

Question 18

Openings/depressions allowing passage of soft tissue or formation of joints: Notch

Answer 18

An indentation at the edge of a structure e.g. scapular notch

Question 19

Openings/depressions allowing passage of soft tissue or formation of joints: Sulcus

Answer 19

A furrow along a bone surface e.g. intertubercular sulcus of the humerus

Question 20

Bone Formation: Ossification

Answer 20

• The formation and remodeling of bone tissue
  
  • Begins during early embryonic development
  • Finishes at the end of life
    Both methods involve the replacement of pre-existing connective tissue wit bone

Question 21

What are the two types of bone ossification?

Answer 21

Intramembranous ossification: Bones form in embryonic tissue membranes. e.g. flat bones of the skull, many bones of the face, mandible and medical clavicle

Endochondral ossification: Bones form in embryonic hyaline cartilage. e.g. all other bones that are not mentioned above

Question 22

What are the bone cells?

Answer 22

• Osteogenic cell: Stem cell that develops into an osteoblast
  
  • Osteoblast: Produces organic components of bone matrix (proteins, collagen) e.g. lays down new bone
  • Osteoclast: Resorbs (removes) bone
    Osteocyte: Maintains bone matrix

Question 23

Intramembranous ossification: Steps 1 and 2

Answer 23

Step 1. Development of the ossification center
- At the site of bone development, and in response to specific chemical messages, mesenchymal cells (stem cells that form connective tissue) cluster together
- Mesenchymal cells differentiate: Osteogenic cells > Osteoblasts
Osteoblasts secrete bone matrix until they are surrounded by it

Step 2: Ossification
- Osteoblasts become trapped in bone matrix > Osteocytes
- Osteocytes sit in lacunae (small cavities)
Calcium and other minerals are deposited and bone matrix hardens (calcifies)

Question 24

Intramembranous ossification: Step 3 and 4

Answer 24

Step 3: Formation of trabeculae
- Blood vessels grow into the area to provide nutrients and delivery of osteoclasts
- Osteoclasts resorb bone and cause the formation of trabeculae (spongey appearance)
Connective tissue associated with blood vessels differentiates into red bone marrow

Step 4: Development of periosteum (hard layer outside a bone)
- Continued bone remodeling forms typical bony product
- Thin layer of compact bone replaces surface layers of trabecular/spongey bone
Mesenchyme condenses at the periphery and develops into the periosteum

Question 25

What is Intramembranous ossification?

Answer 25

Bone formation within the embryonic tissue membranes

Question 26

What is endochondral ossification?

Answer 26

- Bone formation within the cartilage model: Long bone example - Forming in a cartilage model - Children still have a lot of bones made of cartilage when born, as they are not hard yet A lot don’t turn hard until years and years old, and bones aren't fully bone until around 30 (depends on individual)

Question 27

Endochondral ossification: Step 1 and 2

Answer 27

Step 1: Development of cartilage model - Mesenchymal cells respond to specific chemical messages and group together in the shape of the future bone - Mesenchymal cells differentiate > chondroblasts (cartilage-forming cells) Chondroblasts secrete cartilage matrix, producing a cartilage model made of hyaline cartilage Step 2: Growth of the cartilage model - Chondroblasts become buried within the cartilage> chondrocytes - Cartilage model grows: Growth in length by continual cell division of chondrocytes and matrix secretion (interstitial growth). Growth in width due to deposition of matrix on the external surface (appositional growth) - Osteogenic cells within the perichondrium differentiate > osteoblasts Osteoblasts lay down superficial bone to form edges of diaphysis

Question 28

Endochondral ossification: Step 3 and 4

Answer 28

Step 3: Development of the primary ossification center - A nutrient artery penetrates cartilage at diaphysis - Osteoblasts enter alongside blood vessels to produce spongy bone template within cartilage model diaphysis (primary ossification center) Bone growth increases and spreads towards both ends of the cartilage model Step 4: Remodeling of the primary ossification center/development of the medullary cavity - Osteoclasts enter via blood vessel and remove the spongey bone template (formation of the medullary cavity) - Osteoblasts lay down new bone to form cortical/compact bone) at the diaphysis Cartilage and bone continues to grow increasing the size of the model

Question 29

Endochondral ossification: Step 5

Answer 29

Step 5: Development of the secondary ossification centers - Blood vessels penetrate the cartilage at the epiphyses (heads) Osteoblasts follow and lay down spongey bone (secondary ossification centers, unlike primary, spongey bone remains in epiphyses (not remodeled into a cavity))

Question 30

Endochondral ossification: Step 6

Answer 30

Step 6: Formation of epiphyseal growth plate - Epiphysis is remodeled to form spongey (trabecular) bone (contains bone marrow) - The line dividing the epiphysis and the metaphysis remains as cartilage until adulthood (specific age varies depending on bone) - While the line is still cartilages = epiphyseal growth plate - Cartilage of the growth plate continues to lengthen the long bone (interstitial growth) - When the line ossifies at adulthood = epiphyseal line - Cartilage on the very ends of the epiphysis remains as cartilage and forms the articular surface - Only fully mature bone at 18-21 - Before then most people still have growth plates - If not growth plate/chondroblasts, it is all fused to bone (no cartilage) so no more growth occurs Ends of epiphyses, articular/hyaline remains cartilage and cartilage surface

Question 31

What happens if a child breaks their growth plate

Answer 31

If a child fractures their growth plate, bone formation is different to bone remodeling/repair, so if the epiphyseal line is broken, then it will be replaced with new bone rather than cartilage, and bone can't grow. Therefore, if the epiphyseal line is broken in the leg, their leg stops growing and will be shorter than the other.

Question 32

Bone remodeling: overview

Answer 32

- Process of bone cells removing old bone and replacing with new bone continuously - In normal circumstances osteoclasts remove bone at the same rate that osteoblasts form new bone (balance) - Disruption of this balance can lead to bone pathology e.g. osteoporosis

Question 33

Bone remodeling process?

Answer 33

1. Osteoclasts attach to the endosteum or periosteum forming a seal at the edges 2. Osteoclasts release lysosomal enzymes and various acids into the sealed pocket 3. The acids dissolve the bone minerals while the lysosomal enzymes break down the organic components 4. Bone resorption (loss) results 5. Following osteoclastic activity, osteoblasts move in the area 6. Osteoblasts deposits minerals and collagen fibers (components of bone extracellular matrix) Bone formation (growth) results

Question 34

Factors effecting bone remodeling:

Answer 34

- If osteoblasts are more active = more bone formation - If osteoclasts are not active = less bone resorption - If osteoclasts are more active = more bone loss If osteoblasts are not active = less bone formation

Question 35

How does Nutrition affect bone remodeling?

Answer 35

- There are large amounts of phosphorus and calcium stored in bones and these minerals are required fort bone growth and remodeling - Several vitamins are involved in bone remodeling as well - Vitamin A: stimulates osteoblast activity and therefore influences bone deposition - Vitamin D: Increases the absorption of calcium and therefore influences bone deposition - Vitamin C: required for collaged synthesis (collage is a major component of bone ECM) - Vitamin B12 and Vitamin K: are required for the synthesis of bone proteins Dietary intake of relevant vitamins and minerals are therefore important for bone remodeling

Question 36

How do hormones impact bone remodeling?

Answer 36

- Human growth hormone (hGH) and insulin-like Growth Factors (IGF) are important for bone growth during childhood - They stimulate osteoblasts, promote synthesis of proteins for new bone and promote cell division in periosteum and at the epiphyseal plate - Sex hormones (estrogen and testosterone) are important for growth spurts at puberty - They stimulate osteoblasts and stimulate synthesis of bone ECM Insulin and thyroid hormone (T3 and T4) both influence an increase in bone deposition across the lifespan

Question 37

How does age and mortality impact bone remodeling?

Answer 37

- Bones stop lengthening when sex hormones stop influencing interstitial growth from epiphyseal growth plate (after puberty) - Cells become less active as we age and it takes more energy to create new bone than it does to remove it - Increase in mineral loss (especially calcium) with increasing age leads to weakening of the bone - Loss of estrogen at menopause slows osteoblast activity and increases osteoclast activity > post-menopausal osteoporosis - Use it or lose it, especially in the elderly > mechanical force/stress encourages bone deposition, no mechanical stress = increased bone loss

Question 38

What do bones and cartilage do?

Answer 38

Support, movement, protection, blood cell production, triglyceride storage, mineral homeostasis

Question 39

Overview on bones:

Answer 39

- Adults - 206 bones - Children - have more, fuse as they develop - Axial: Cranial bones and spine: 80 - Appendicular: Bones in limbs and pelvic, pectoral and shoulder girdle: 126 bones 5 types:

Question 40

What are long bones?

Answer 40

Longer than they are wide: Humerus, radius, upper arm, ulna, femur, thig, tibia, tibia, phalanges

Question 41

What are short bones?

Answer 41

Equal in length and width, cube shaped: Tarsal, ankle, carpal, wrist, thin external layer of compact bone but mostly spongey bone

Question 42

What are flat bones?

Answer 42

Thin, spongey enclose by two plates of hard bone almost parallel: Cranial, ribs, sternum, Capula

Question 43

What are irregular bones?

Answer 43

Complex shape: Pelvic, some facial, vertebrae, heel bone, vary in composition of compact and spongey

Question 44

What are sesamoid bones?

Answer 44

Some tendons with friction and physical stress, wear and tear. Sesame seed shaped, patella/ knee cap, only a few millimeters, palms and soles of feet, some are not completely ossified

Question 45

Diaphysis and Metaphysis:

Answer 45

- Diaphysis: Shaft, slightly curved for stress of weight baring and prevent fracture Metaphysis: in between Diaphysis and Epiphysis, growing bone, contains growth plate

Question 46

Epiphyseal line, Articular cartilages and Periosteum:

Answer 46

- Structure replacing the epiphyseal plate is the epiphyseal line - Articular cartilages: End of bone to bone, assists with shock absorption and friction Periosteum covers the bones that is not covered by articular cartilage, tough connective tissue, inner and outer layer, protects bone, nourishes, assist in repair, attaches to bone

Question 47

Medullary, Endosteum:

Answer 47

- Medullary: Hollow, diaphysis, contains marrow and blood vessels in adults, minimized weight of bone - Endosteum: thin membrane composed of a single layer of bone forming cells, lie sin medullar, involved in bone remodeling

Question 48

What do synovial joints do?

Answer 48

- Joint/synovial cavity between articulating bones - Allows movement - Bones articulating surfaces at the synovial joint are covered in hyaline cartilage/articular cartilage - Provides smooth slippery surface, but does not bine surfaces together, reduces friction, allows for shock absorption - Sleeve structure around synovial joint: joint capsule - Inner synovial membrane: areolar connective tissue, elastic fibers Outer fibrous membrane: thickened continuation of the periosteum, and is collagen rich dense connective tissue

Question 49

Intra and extra scapular ligaments:

Answer 49

- Intracapsular ligaments: in joint space, separate to fluid e.g. anterior and posterior cruciate ligaments Extracapsular ligaments: outside joint capsule e.g. medial, lateral ligaments of knee

Question 50

Menisci, Labrum, intervertebral discs:

Answer 50

- Menisci: discs in some synovial joints such as knee, wrist and jaw. Crescent shaped pads of fibro cartilage between joint surfaces and attached to joint capsules, improves articulation of bony surfaces, weight distribution, distribution of synovial fluid, shock absorptions - Labrum: shoulder, hip, deepens joint socket increasing contact area between articulating surfaces Intervertebral discs: sit between vertebrae, outer fibrous ring, nucleus polyposis, elastic substance in the anulus fibrosis, thin layer of cartilage. Allow movements of spine, form strong joints, vertical shock, discs compress during the day

Question 51

Plane joints:

Answer 51

- Biaxial or triaxial - Allows movements in two axes - Allows for gliding, or back and forth or side to side Found in-between carpals, intertarsal between tarsals in ankle, sternoclavicular, sternocostal, vertebrae costal joints

Question 52

Pivot Joint:

Answer 52

- Uniaxial, one axis - Rotation only around its longitudinal axis - Permits head to turn from side to side Ulna joint, palms to turn anteriorly and posteriorly

Question 53

Hinge joint:

Answer 53

- Uniaxial movement - Flexion, extension Knee, elbow, ankle and interphalangeal joints (fingers and toes)

Question 54

Condyloid joint:

Answer 54

- Biaxial movement - Flexion, extension, abduction, adduction - Limited circumduction (not isolated movement) - Radiocarpal joint at wrist, '

Question 55

Saddle joint:

Answer 55

- Biaxial - Allow movement in two directions - Flexion, extension, abduction, adduction - Limited circumduction Metacarpal, carpus

Question 56

Ball and Socket joint:

Answer 56

- Triaxial movement - Three axes - Flexion, extension, abduction adduction, rotation - Shoulder, hip joint

Question 57

Bone resorption:

Answer 57

osteoclasts remove collagen fibers and minerals from bone tissue. Attach to endosteum or periosteum forming a seal at edges, put enzymes into pocket created, acids dissolve bone minerals. Minerals From ECM and bone proteins pass through osteoclast into the interstitial fluid and into the capillaries

Question 58

Bone Deposition:

Answer 58

Osteoblasts provide collagen fibers and minerals. Bone ECM

Question 59

What is bone remodeling influence by?

Answer 59

- Remodeling is influenced by: Minerals (phosphorus, calcium, magnesium, manganese, fluoride. Vitamins (A, B12, C, D, K). Hormones (insulin like growth factors, insulin, thyroid hormones, human growth hormones) - In children, more bone deposition than loss, which results in bone growth - Sex hormones create growth spurt during puberty: antigen's, estrogens, these increase osteoblast activity and synthesis of bone ECM Bone stop lengthening when sex hormones (estrogens) stop growth at the epiphyseal or growth plate, hence why growth in females ends before males

Question 60

What is de-mineralization?

Answer 60

Loss of minerals (8% of bone mass each decade for women)=, for men = 3% each decade after 60

Question 61

What is brittleness?

Answer 61

Susceptible to fractures, decrease rate of protein synthesis as we age, causes lack of bone density and frailness Can lead to loss of teeth, height, pain

Question 62

What are the two criteria for structural classification of joints?

Answer 62

- Presence or absence of a space between articulating bones The type of connective tissue that binds the bone together

Question 63

With respect to bone formation, match the (A) type of ossification, with (B) its correct description.

Answer 63

(A) Endochondral ossification (B) Bone formation within the cartilage model

Question 64

Given that only the diaphyses of Jack's bones are visible, what stage of bone formation does this suggest he has reached?

Answer 64

Primary ossification

Question 65

What classification does the wrist joint belong to?

Answer 65

Synovial joint

Question 66

What bones predominantly make up the wrist joint?

Answer 66

Carpals and radius

Question 67

What specific kind of joint is the wrist joint?

Answer 67

Condyloid

Question 68

Regarding normal bone remodelling, which option is correct with respect to (A) the cell type, and (B) its corresponding function?

Answer 68

(A) Osteoblasts (B) Deposit minerals and collagen fibres (components of bone ECM)

Question 69

What are the 3 types of structural joints? What are the 6 types of synovial joints?

Answer 69

What re the 6 types of synovial joints? - Hinge, pivot, ball and socket, saddle, condyloid, plane What are the three types of structural classification of joints? - Cartilaginous - Fibrous Synovial

Question 70

Degree of congruency in hip and shoulder joints?

Answer 70

Hip joint is more congruent than shoulder prioritizing stability for weight baring, while the shoulder favors mobility and range of motion

Question 71

Degree of congruency in comparing knee and elbow joint?

Answer 71

The elbow has a higher degree of congruency than the knee prioritizing stability for controlled movement, while the knee with moderate congruency balances stability and flexibility to accommodate weight baring and range of motion

Question 72

What is joint congruence

Answer 72

A congruent joint is where the bone ends fit well An incongruent joint is where the bone ends do not fit well

Question 73

What happens if bones fit well/don't fit well together

Answer 73

Bone ends fit well together Joint more stable Not as reliant on other structures Less likely to slip (dislocate) Bone ends don’t fit well together Joint less stable Need other structures to hold the joint in place Ligaments, muscles/tendons Hip joint

Question 74

Classification of joints?

Answer 74

Synarthorsis: Immobile or limited mobility (fibrous joints) Amphiarthrosis: Small about of mobility (cartilaginous joints) Diarthrosis: Freely moving (synovial joints)

Question 75

Movement at: Fibrous joints Cartilaginous joints Synovial joints

Answer 75

Movement at fibrous joints: Depends on the length of fibers uniting the bones Generally little to no movement Movement: some to none Types: Primary = synchondrosis Secondary = symphysis Synovial joints Definition A joint which has: 1. Hyaline cartilage covering bone ends 2. A joint cavity containing synovial fluid 3. A synovial membrane 4. A fibrous capsule Synovial joints 5, Reinforced by ligaments 6. Have rich blood and nerve supply

Question 76

Primary and secondary cartilaginous joints

Answer 76

Primary cartilaginous joint Bones joined by hyaline cartilage Can be temporary Epiphyseal plate of developing bones Can be permanent Where costal cartilage of the first rib joins the manubrium (= 1st sternocostaljoint) Secondary cartilaginous joints Articular surfaces covered by hyaline cartilage and joined by fibrocartilage Strong joints – limited movement Pubic symphysis Manubriosternal joint Anterior intervertebral joints