The Skeletal System. Yong Jeong, MD, PhD Department of Bio and Brain Engineering

Transcription

1 5 The Skeletal System Yong Jeong, MD, PhD Department of Bio and Brain Engineering The Skeletal System Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments Two subdivisions of the skeleton Axial skeleton Appendicular skeleton 1

2 Functions of Bones Support the body Protect soft organs Allow movement due to attached skeletal muscles Store minerals and fats Blood cell formation Bones of the Human Body The adult skeleton has 206 bones Two basic types of bone tissue Compact bone Homogeneous Spongy bone Small needle-like pieces of bone Many open spaces Figure 5.2b 2

3 Classification of Bones on the Basis of Shape Figure 5.1 Classification of Bones Long bones Typically longer than they are wide Have a shaft with heads at both ends Contain mostly compact bone Example: Femur Humerus 3

4 Classification of Bones Figure 5.1a Classification of Bones Short bones Generally cube-shape Contain mostly spongy bone Example: Carpals Tarsals 4

5 Classification of Bones Figure 5.1b Classification of Bones Flat bones Thin, flattened, and usually curved Two thin layers of compact bone surround a layer of spongy bone Example: Skull Ribs Sternum 5

6 Classification of Bones Figure 5.1c Classification of Bones Irregular bones Irregular shape Do not fit into other bone classification categories Example: Vertebrae Hip bones 6

7 Classification of Bones Figure 5.1d Anatomy of a Long Bone Diaphysis Shaft Composed of compact bone Epiphysis Ends of the bone Composed mostly of spongy bone 7

8 Anatomy of a Long Bone Figure 5.2a Anatomy of a Long Bone Periosteum Outside covering of the diaphysis Fibrous connective tissue membrane Sharpey s fibers Secure periosteum to underlying bone Arteries Supply bone cells with nutrients 8

9 Anatomy of a Long Bone Figure 5.2c Anatomy of a Long Bone Articular cartilage Covers the external surface of the epiphyses Made of hyaline cartilage Decreases friction at joint surfaces 9

10 Anatomy of a Long Bone Epiphyseal plate Flat plate of hyaline cartilage seen in young, growing bone Epiphyseal line Remnant of the epiphyseal plate Seen in adult bones Anatomy of a Long Bone Medullary cavity Cavity inside of the shaft Contains yellow marrow (mostly fat) in adults Contains red marrow (for blood cell formation) in infants 10

11 Bone Markings Surface features of bones Sites of attachments for muscles, tendons, and ligaments Passages for nerves and blood vessels Categories of bone markings Projections or processes grow out from the bone surface Depressions or cavities indentations Bone Markings Table 5.1 (1 of 2) 11

12 Bone Markings Notch Indentation at the edge of the structure Table 5.1 (2 of 2) Microscopic Anatomy of Bone Osteon (Haversian system) A unit of bone containing central canal and matrix rings Central (Haversian) canal Opening in the center of an osteon Carries blood vessels and nerves Perforating (Volkman s) canal Canal perpendicular to the central canal Carries blood vessels and nerves 12

13 Microscopic Anatomy of Bone Figure 5.3a Microscopic Anatomy of Bone Lacunae Cavities containing bone cells (osteocytes) Arranged in concentric rings Lamellae Rings around the central canal Sites of lacunae 13

14 Microscopic Anatomy of Bone Figure 5.3b c Microscopic Anatomy of Bone Canaliculi Tiny canals Radiate from the central canal to lacunae Form a transport system connecting all bone cells to a nutrient supply 14

15 Microscopic Anatomy of Bone Figure 5.3b Formation of the Human Skeleton In embryos, the skeleton is primarily hyaline cartilage During development, much of this cartilage is replaced by bone Cartilage remains in isolated areas Bridge of the nose Parts of ribs Joints 15

16 Bone Growth (Ossification) Epiphyseal plates allow for lengthwise growth of long bones during childhood New cartilage is continuously formed Older cartilage becomes ossified Cartilage is broken down Enclosed cartilage is digested away, opening up a medullary cavity Bone replaces cartilage through the action of osteoblasts Long Bone Formation and Growth Hyaline cartilage Articular cartilage Spongy bone New center of bone growth Bone starting to replace cartilage Bone collar Hyaline cartilage model Medullary cavity Growth in bone length Epiphyseal plate cartilage Blood vessels New bone forming Epiphyseal plate cartilage New bone forming Growth in bone width In an embryo In a fetus In a child (a) Figure 5.4a, step 3 16

17 Bone Growth (Ossification) Bones are remodeled and lengthened until growth stops Bones are remodeled in response to two factors Blood calcium levels Pull of gravity and muscles on the skeleton Bones grow in width (called appositional growth) Long Bone Formation and Growth Figure 5.4b 17

18 Types of Bone Cells Osteocytes mature bone cells Osteoblasts bone-forming cells Osteoclasts bone-destroying cells Break down bone matrix for remodeling and release of calcium in response to parathyroid hormone Bone remodeling is performed by both osteoblasts and osteoclasts Bone Fractures Fracture break in a bone Types of bone fractures Closed (simple) fracture break that does not penetrate the skin Open (compound) fracture broken bone penetrates through the skin Bone fractures are treated by reduction and immobilization 18

19 Common Types of Fractures Table 5.2 Repair of Bone Fractures Hematoma (blood-filled swelling) is formed Break is splinted by fibrocartilage to form a callus Fibrocartilage callus is replaced by a bony callus Bony callus is remodeled to form a permanent patch 19

20 Stages in the Healing of a Bone Fracture Hematoma Internal callus (fibrous tissue and cartilage) External callus New blood vessels Bony callus of spongy bone Healed fracture Spongy bone trabecula Hematoma formation Fibrocartilage callus formation Bony callus formation Bone remodeling Figure 5.5, step 4 The Axial Skeleton Forms the longitudinal axis of the body Divided into three parts Skull Vertebral column Bony thorax 20

21 The Axial Skeleton Figure 5.6a The Axial Skeleton Figure 5.6b 21

22 The Skull Two sets of bones Cranium Facial bones Bones are joined by sutures Only the mandible is attached by a freely movable joint Human Skull, Lateral View Figure

23 Human Skull, Superior View Figure 5.8 Human Skull, Inferior View Figure

24 Human Skull, Anterior View Figure 5.11 Paranasal Sinuses Hollow portions of bones surrounding the nasal cavity Functions of paranasal sinuses Lighten the skull Give resonance and amplification to voice 24

25 Paranasal Sinuses Figure 5.10a Paranasal Sinuses Figure 5.10b 25

26 The Hyoid Bone The only bone that does not articulate with another bone Serves as a moveable base for the tongue Aids in swallowing and speech The Hyoid Bone Figure

27 The Fetal Skull The fetal skull is large compared to the infant s total body length Fontanels fibrous membranes connecting the cranial bones Allow the brain to grow Convert to bone within 24 months after birth The Fetal Skull Figure 5.13a 27

28 The Fetal Skull Figure 5.13b The Vertebral Column Each vertebrae is given a name according to its location There are 24 single vertebral bones separated by intervertebral discs Seven cervical vertebrae are in the neck Twelve thoracic vertebrae are in the chest region Five lumbar vertebrae are associated with the lower back 28

29 The Vertebral Column Nine vertebrae fuse to form two composite bones Sacrum Coccyx The Vertebral Column Figure

30 The Vertebral Column The spine has a normal curvature Primary curvatures are the spinal curvatures of the thoracic and sacral regions Present from birth Secondary curvatures are the spinal curvatures of the cervical and lumbar regions Develop after birth The Vertebral Column Figure

31 A Typical Vertebrae, Superior View Figure 5.17 Regional Characteristics of Vertebrae Figure 5.18a 31

32 Regional Characteristics of Vertebrae Figure 5.18b Regional Characteristics of Vertebrae Figure 5.18c 32

33 Regional Characteristics of Vertebrae Figure 5.18d Sacrum and Coccyx Sacrum Formed by the fusion of five vertebrae Coccyx Formed from the fusion of three to five vertebrae Tailbone, or remnant of a tail that other vertebrates have 33

34 Sacrum and Coccyx Figure 5.19 The Bony Thorax Forms a cage to protect major organs Consists of three parts Sternum Ribs True ribs (pairs 1 7) False ribs (pairs 8 12) Floating ribs (pairs 11 12) Thoracic vertebrae 34

35 The Bony Thorax Figure 5.20a The Appendicular Skeleton Composed of 126 bones Limbs (appendages) Pectoral girdle Pelvic girdle 35

36 The Appendicular Skeleton Figure 5.6a The Appendicular Skeleton Figure 5.6b 36

37 The Pectoral (Shoulder) Girdle Composed of two bones Clavicle collarbone Scapula shoulder blade These bones allow the upper limb to have exceptionally free movement Bones of the Shoulder Girdle Figure 5.21a 37

38 Bones of the Shoulder Girdle Figure 5.21b Bones of the Shoulder Girdle Figure 5.21c d 38

39 Bones of the Upper Limbs Humerus Forms the arm Single bone Bones of the Upper Limbs Figure 5.22a b 39

40 Bones of the Upper Limbs The forearm has two bones Ulna Medial bone in anatomical position Radius Lateral bone in anatomical position Bones of the Upper Limbs Figure 5.22c 40

41 Bones of the Upper Limbs The hand Carpals wrist Metacarpals palm Phalanges fingers Bones of the Upper Limbs Figure

42 Bones of the Pelvic Girdle Formed by two coxal (ossa coxae) bones Composed of three pairs of fused bones Ilium Ischium Pubis Bones of the Pelvic Girdle The total weight of the upper body rests on the pelvis It protects several organs Reproductive organs Urinary bladder Part of the large intestine 42

43 The Pelvis Figure 5.24a The Pelvis: Right Coxal Bone Figure 5.24b 43

44 Gender Differences of the Pelvis The female inlet is larger and more circular The female pelvis as a whole is shallower, and the bones are lighter and thinner The female ilia flare more laterally The female sacrum is shorter and less curved The female ischial spines are shorter and farther apart; thus the outlet is larger The female pubic arch is more rounded because the angle of the pubic arch is greater Gender Differences of the Pelvis Figure 5.24c 44

45 Bones of the Lower Limbs The thigh has one bone Femur The heaviest, strongest bone in the body Bones of the Lower Limbs Figure 5.25a b 45

46 Bones of the Lower Limbs The lower leg has two bones Tibia Shinbone Larger and medially oriented Fibula Thin and sticklike Bones of the Lower Limbs Figure 5.25c 46

47 Bones of the Lower Limbs The foot Tarsals Two largest tarsals Calcaneus (heelbone) Talus Metatarsals sole Phalanges toes Bones of the Lower Limb Figure

48 Arches of the Foot Bones of the foot are arranged to form three strong arches Two longitudinal One transverse Arches of the Foot Figure

49 Joints Articulations of bones Functions of joints Hold bones together Allow for mobility Ways joints are classified Functionally Structurally Functional Classification of Joints Synarthroses Immovable joints Amphiarthroses Slightly moveable joints Diarthroses Freely moveable joints 49

50 Structural Classification of Joints Fibrous joints Generally immovable Cartilaginous joints Immovable or slightly moveable Synovial joints Freely moveable Summary of Joint Classes [Insert Table 5.3 here] Table

51 Fibrous Joints Bones united by fibrous tissue Example: Sutures Syndesmoses Allows more movement than sutures Example: Distal end of tibia and fibula Fibrous Joints Figure 5.28a b 51

52 Cartilaginous Joints Bones connected by cartilage Example: Pubic symphysis Intervertebral joints Cartilaginous Joints Figure 5.28c e 52

53 Synovial Joints Articulating bones are separated by a joint cavity Synovial fluid is found in the joint cavity Synovial Joints Figure 5.28f h 53

54 Features of Synovial Joints Articular cartilage (hyaline cartilage) covers the ends of bones A fibrous articular capsule encloses joint surfaces A joint cavity is filled with synovial fluid Ligaments reinforce the joint Structures Associated with the Synovial Joint Bursae flattened fibrous sacs Lined with synovial membranes Filled with synovial fluid Not actually part of the joint Tendon sheath Elongated bursa that wraps around a tendon 54

55 The Synovial Joint Figure 5.29 Types of Synovial Joints Figure 5.30a c 55

56 Types of Synovial Joints Figure 5.30d f Inflammatory Conditions Associated with Joints Bursitis inflammation of a bursa usually caused by a blow or friction Tendonitis inflammation of tendon sheaths Arthritis inflammatory or degenerative diseases of joints Over 100 different types The most widespread crippling disease in the United States 56

57 Clinical Forms of Arthritis Osteoarthritis Most common chronic arthritis Probably related to normal aging processes Rheumatoid arthritis An autoimmune disease the immune system attacks the joints Symptoms begin with bilateral inflammation of certain joints Often leads to deformities Clinical Forms of Arthritis Gouty arthritis Inflammation of joints is caused by a deposition of uric acid crystals from the blood Can usually be controlled with diet 57

58 Developmental Aspects of the Skeletal System At birth, the skull bones are incomplete Bones are joined by fibrous membranes called fontanels Fontanels are completely replaced with bone within two years after birth Ossification Centers in a 12-week-old Fetus Figure

59 Skeletal Changes Throughout Life Fetus Birth Long bones are formed of hyaline cartilage Flat bones begin as fibrous membranes Flat and long bone models are converted to bone Fontanels remain until around age 2 Skeletal Changes Throughout Life Adolescence Epiphyseal plates become ossified and long bone growth ends Size of cranium in relationship to body 2 years old skull is larger in proportion to the body compared to that of an adult 8 or 9 years old skull is near adult size and proportion Between ages 6 and 11, the face grows out from the skull 59

60 Skeletal Changes Throughout Life Figure 5.33a Skeletal Changes Throughout Life Figure 5.33b 60

61 Skeletal Changes Throughout Life Curvatures of the spine Primary curvatures are present at birth and are convex posteriorly Secondary curvatures are associated with a child s later development and are convex anteriorly Abnormal spinal curvatures (scoliosis and lordosis) are often congenital Skeletal Changes Throughout Life Figure

62 Skeletal Changes Throughout Life Osteoporosis Bone-thinning disease afflicting 50% of women over age 65 20% of men over age 70 Disease makes bones fragile and bones can easily fracture Vertebral collapse results in kyphosis (also known as dowager s hump) Estrogen aids in health and normal density of a female skeleton Skeletal Changes Throughout Life Figure

63 Skeletal Changes Throughout Life Figure