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The Skeletal System Chapter 6.

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Presentation on theme: "The Skeletal System Chapter 6."— Presentation transcript:

1 The Skeletal System Chapter 6

2 Bone Function Support Protection Leverage- for motion
Mineral Homeostasis Blood cell production Hemopoiesis in red bone marrow Triglyceride Storage

3 Types of Bones Long bones- longer than wide
e.g. thigh, leg, arm, forearm, fingers & toes Short bones- almost cube shaped Most wrist & ankle bones Flat bones- thin & extensive surface E.g. Cranial bones sternum, ribs & scapulae Irregular bones- don’t fit above E.G vertebrae and some facial bones

4 Macroscopic Structure
Parts of a long bone: Diaphysis Epiphysis Metaphysis Articular cartilage Periosteum Medullary cavity Endosteum

5 Figure 6.1a

6 Figure 6.1b

7 Microscopic Structure
Matrix= 25% water, 25% collagen fibers, 50% crystallized mineral salts Osteogenic cells- in periosteum Osteoblasts- secrete collagen fibers- Build matrix and become trapped in lacunae Become osteocytes- maintain bone Osteoclasts –formed from monocytes Digest bone matrix for Normal bone turnover

8 Compact Bone Structure
few spaces, right below periosteum Units = osteons (Haversian system) Central canal- blood vessels, nerves, lymphatics Concentric lamellae- layers of matrix Lacunae- “lakes” contain osteocytes Canaliculae- little canals nutrient flow from canals and between osteocytes

9 Figure 6.2a

10 Spongy Bone units containing trabeculae
spaces between trabeculae often contain Red Marrow No osteons but include lacunae & canaliculae

11 Figure 6.2b

12 Bone Formation Ossification 1. initially in embryo & fetus 2. Growth
3. remodeling 4. repair of fractures

13 Bone Formation Mesenchyme model - replaced with bone
Intramembranous - Bone forms directly in mesenchyme layers (membrane like) Endochondrial - forms within hyaline cartilage developed from mesenchyme

14 Intramembranous Ossification
Development of ossification center- Cells differentiate=> osteogenic=> osteoblasts Osteoblasts secrete organic matrix Calcification- cells become osteocytes In lacunae they extend cytoplasmic processes to each other Deposit calcium & other mineral salts Formation of trabeculae- spongy bone Blood vessels grow in and red marrow is formed Mesenchyme=> periosteum

15 Endochondrial Ossification
Develop a cartilage model- Growth- chondroblasts secrete cartilage Perichondrium forms on surface Internal chondrocytes in lacunae die and form small cavities

16 Figure 6.3

17 Endochondrial Ossification
Ossification proceeds inward with nutrient artery from surface perichondrium In disintegrating cartilage osteogenic cells=> osteoblasts and create a primary ossification center As bone forms perichondrium => periosteum

18 Endochondrial Ossification
First spongy bone is formed Osteoblasts breaks some down=> Center develops a cavity wall of diaphysis => compact bone Near birth, blood vessels enter epiphysis Secondary center is developed Hyaline cartilage at end => articular cartilage

19 Figure 6.4

20 Growth Length- chondrocytes in the epiphyseal plate divide and increase cartilage layer On diaphyseal side they die and are replaced by bone Stops during adolescence Periosteum supports surface growth for thickness

21 Remodeling & Repair Remodeling in response to use-
resorption by osteoclasts and deposition by osteoblasts Repair after a fracture Dead tissue removed Chondroblasts => fibrocartilage => spongy bone by osteoblasts => remodeled to compact bone

22 Types of Fractures Partial- incomplete break (crack)
Complete- bone in two or more pieces Closed (simple)- not through skin Open (compound)- broken ends break skin

23 Factors Affecting Growth
Adequate minerals (Ca, Mg, P) Vitamins A, C, D Hormones Before puberty: hGH + insulin-like growth factors Thyroid hormone & insulin also required Sex steroids help adolescent growth spurt and cause closure of epiphyseal plate. Weight-bearing activity

24 Calcium Homeostasis Blood levels of Ca2+ controlled
Negative feedback loops Parathyroid hormone => increased osteoclast activity + decreased loss in urine Calcitonin=> decreased osteoclast activity

25 Figure 6.5

26 Exercise & Bone Tissue Bone strengthened in response to use
Reabsorbed during disuse e.g. Bone loss during bed rest, fractures in cast, astronauts with no gravity

27 Divisions of Skeletal System
Two divisions: axial & appendicular Axial- around body axis E.g. head, hyoid, ribs, sternum, & vertebrae Appendicular- bones of upper & lower limbs plus girdles that connect them

28 Figure 6.6

29 Skull & Hyoid bone Facial bones: Cranial bones:
Frontal, 2 parietal, 2 temporal, occipital, sphenoid, and ethmoid Facial bones: 2 nasal, 2 maxillae, 2 zygomatic, mandible, 2 lacrimal, 2 paltine, 2 inferior nasal conchae, & the vomer

30 Figure 6.7a

31 Figure 6.7b

32 Figure 6.7c

33 Figure 6.8

34 Figure 6.9

35 Figure 6.10a

36 Figure 6.10b

37 Unique Features of Skull
Sutures- immoveable joint between skull bones Coronal, sagittal, lambdoidal, squamous Paranasal sinuses-cavities Located in bones near nasal cavity Fontanels- soft spot in fetal skull Allow deformation at birth Calcify to form sutures

38 Figure 6.11

39 Vertebrae Encloses spinal cord Supports head
Point of attachment for muscles of back, ribs and pelvic girdle 7 cervical 12 thoracic 1 sacrum & 1 coccyx

40 Normal Curves in Column
Relative to front: cervical & lumbar curves are convex Thoracic & sacral curves are concave They increase strength, help in balance and absorb shocks

41 Figure 6.12a

42 Figure 6.12b

43 Structure of Vertebra Body- disc-shaped front part
Vertebral arch- extends back from body creates with the body a hole called vertebral foramen 7 processes- Transverse process extending laterally on each side Spinous process extending dorsally Two each of Superior and inferior articular processes- attach to neighboring vertebrae

44 Figure 6.13

45 Cervical Area region is number from top to bottom Cervical (C1-C7)
Spinous process often bifid and have transverse foramina on transverse process C1- specialized to support head- called the atlas- articulates with head Lacks body and spinous process C2 – axis- has body & spinous process Also dens- that creates a pivot for head rotation

46 Figure 6.14

47 Other Vertebrae Thoracic (T1-T12 ) Lumbar (L1-L5)
Larger than cervical Have facets for articulating with ribs Lumbar (L1-L5) Largest & strongest. Processes short & thick Sacrum (S1-S5 fused to one unit) Foundation for pelvic girdle Contain sacral foramina for nerves and blood vessels Coccyx- 4 fused coccygeal vertebrae

48 Figure 6.12a

49 Figure 6.12b

50 Figure 6.15

51 Figure 6.16

52 Thorax Thoracic cage = Sternum, costal cartilages & ribs and bodies of T1-T12 Sternum- form by 3 bones that fuse by age ~25yrs = manubrium, body, xiphoid process Ribs- 12 pairs 1-7 articulate with sternum directly costal cartilage= true ribs

53 Figure 6.17

54 Pectoral Girdle Attach bones of upper limbs to axial skeleton
Right & left Clavicle & Scapula

55 Figure 6.18

56 Upper Limb Humerus = arm bone Articulates with scapula at shoulder
Articulates with radius & ulna at elbow Ulna – medial bone Radius- lateral bone (thumb side)

57 Figure 6.19

58 Figure 6.20a

59 Figure 6.20b

60 Wrist & Hand Carpus (wrist) -8 bones Metacarpals – 5 bones of hand
Number 1-5 starting with thumb Phalanges- 14 bones of fingers Numbered like metacarpals each finger but the thumb has proximal, medial & distal Thumb only proximal & distal

61 Figure 6.21

62 Pelvic Girdle Pelvic girdle includes two hip bones
Joined in front at pubic symphysis At back- attached to sacrum = sacroiliac joint Pelvic (hip) bone also called coxal bones

63 Figure 6.22a

64 Figure 6.22b

65 Parts of Coxal Bones 3 bones fuse by age 23 to form coxal
Ilium- largest & most superior Ischium- lower posterior part Pubis lower anterior part

66 Figure 6.23

67 Lower Limb Femur- thigh bone Patella = kneecap in front of knee joint
Articulates with hip proximally and the tibia and fibula distally Patella = kneecap in front of knee joint Tibia- large medial, weight bearing bone of leg Fibula- lateral to tibia and smaller

68 Figure 6.24

69 Figure 6.25

70 Ankle & Foot Tarsus (ankle) has 7 bones Metatarsals (foot bones)
Large talus (ankle bone) and Calcaneus (heel bone) Metatarsals (foot bones) Numbered from medial to lateral Phalanges (toe bones) Big toe has proximal and distal phalanges while others have proximal, medial and distal phalanges. Numbered like metatarsals

71 Figure 6.26

72 Figure 6.27

73 Male & Female Differences
Males usually have heavier bones Related to muscle size & strength Female pelvis is wider and shallower than the males- allows for birth

74 Aging & Skeletal System
Birth through adolescence more bone formed than lost Young adults- gain & loss about equal As levels of sex steroids decline with age: bone resorption > bone formation Bones become brittle and lose Calcium

75 Figure 6.28

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