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Unit 4 The Skeletal System Lecture 1- Bone Structure, Formation and Growth (Chapters 7 & 8)

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Presentation on theme: "Unit 4 The Skeletal System Lecture 1- Bone Structure, Formation and Growth (Chapters 7 & 8)"— Presentation transcript:

1 Unit 4 The Skeletal System Lecture 1- Bone Structure, Formation and Growth (Chapters 7 & 8)

2 The Skeletal System- Overview  The skeleton contains 206 bones  Parts of the skeletal system  Bones (skeleton)  Joints  Cartilages  Ligaments (bone to bone)  Divided into two divisions  Axial skeleton  Appendicular skeleton – limbs and girdle

3 Classification of Bones on the Basis of Shape Figure 5.1

4 Classification of Bones- Shape  Long bones  Typically longer than wide  Have a shaft with heads at both ends  Contain mostly compact bone Examples: Femur, humerus

5 Classification of Bones- Shape  Short bones  Generally cube-shape  Contain mostly spongy bone  Examples: Carpals, tarsals  Sesamoid bones  Small, round  Example: patella

6 Classification of Bones- Shape  Flat bones  Thin and flattened  Usually curved  Thin layers of compact bone around a layer of spongy bone  Examples: Skull, ribs, sternum

7 Classification of Bones- Shape  Irregular bones  Irregular shape  Do not fit into other bone classification categories  Example: Vertebrae and hip

8 Classification of Bones on the Basis of Shape

9 Classification of Bones- Markings  Projections  grow out from a bone surface  site of muscle and ligament attachments  help form joints  Examples: process, crest, facet, ramus, condyle

10 Classification of Bones- Markings  Openings  Hollows, cavities or passageways  allow blood vessels and nerves to pass through  Examples: sinus, meatus, foramen, groove, fissure  Depressions  Indentations  articulates with a process  Examples: fossa

11 Functions of Bones  Support of the body  Protection of soft organs  Movement due to attached skeletal muscles  Storage of minerals and fats  Blood cell formation

12 Mineral Storage  Bone matrix is made of collagen and inorganic mineral salts  Salt = 70% of matrix weight  Mostly calcium phosphate  Calcium is vital in the body  Muscle cell contraction  Nerve impulse conduction  Blood clot formation  Low blood calcium = osteoclasts break down bone  High blood calcium = osteoblasts form bone

13 Blood Cell Formation  Process of blood cell formation is called hematopoiesis  Begins in yolk sac, outside of embryo  Blood cells are later manufactured in the live and spleen  Eventually form bone marrow  Marrow is a soft mass of connective tissue

14 Blood Cell Formation  Types of Marrow:  Red Marrow  Forms blood cells (red, white and platelets)  Yellow Marrow  Stores fat  Does not produce blood cells  Marrow distribution changes with age  Infants- most marrow is red  Over time yellow marrow replaces red marrow  Adults- red marrow found in spongy bone of skull, ribs, sternum, clavicle, vertebrae and hips

15 Bone Tissue  Two basic types of bone tissue  Compact bone  Homogeneous  Dense  Outer bone  Spongy bone  Small needle-like pieces of bone  Many open spaces, porous  Inner bone

16 Gross Anatomy of a Long Bone  Diaphysis  Shaft  Composed of compact bone  Epiphysis  Ends of the bone  Composed mostly of spongy bone  Metaphysis  Between diaphysis and epiphysis


18 Structures of a Long Bone  Periosteum  Outside covering of the diaphysis  Fibrous connective tissue membrane  Endosteum  Lines medullary cavity  Sharpey’s fibers  Secure periosteum to underlying bone  Arteries  Supply bone cells with nutrients

19 Structures of a Long Bone  Medullary cavity  Cavity of the shaft  Contains yellow marrow (mostly fat) in adults  Contains red marrow (for blood cell formation) in infants

20 Structures of a Long Bone  Articular cartilage  Covers the external surface of the epiphyses  Made of hyaline cartilage  Decreases friction at joint surfaces

21 Microscopic Anatomy of Bone  Osteon  A unit of bone  Central (Haversian) Canal  Opening in the center of an osteon  Carries blood vessels and nerves

22 Microscopic Anatomy of Bone  Lacunae  Cavities containing bone cells (osteocytes)  Arranged in concentric rings  Lamellae  Rings around the central canal  Sites of lacunae  Canaliculi  Tiny canals  Connect lacunae

23 Microscopic Anatomy of Bone Figure 5.3

24 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  Bone remodeling is a process by both osteoblasts and osteoclasts

25 Osteoblast Osteocyte Osteoclast Eats bone Builds new bone Mature bone cell


27 Bone Development and Growth  Osteogenesis- development of bone  Intramembranous bones  originate within layers of connective tissue  Flat bones of skull, clavicles, sternum and some facial bones  Endochondral bones  Develop from hyaline cartilage  Shaped like future bones  Initial growth is rapid

28 Endochondral Bone Formation 1.Perichondrium becomes a periosteum and a bone collar forms around the cartilage model. 2.Cavity begins to form within cartilage. 3.Periosteal bud invades marrow cavity. 4.Osteoblasts lay down spongy bone in the bone interior. 5.Osteoclast eventually remove the spongy bone and leave a cavity to house fat.

29 Endochondral Bone Formation

30 Bone Development and Growth- Fetus  The skeleton begins to form during the first few weeks of prenatal development  In embryos, the skeleton is primarily hyaline cartilage  Cartilage remains in isolated areas  Bridge of the nose  Parts of ribs  Joints  Bone structures continue to develop into adulthood

31 Fetal Skeleton 275 bones 12 weeks (6-9 inches long)

32 Bone Growth in Childhood  Epiphyseal plates allow for growth of long bone during childhood  New cartilage is continuously formed  Older cartilage becomes ossified  Cartilage is broken down  Bone replaces cartilage

33 Long Bone Formation and Growth

34 Bone Growth in Adulthood  Bone formation and growth stops between years of age  Bone remodeling continues throughout life  Osteoclasts resorb bone tissue  Osteoblasts replace/deposit new bone  10%-20% of the skeleton is replaced annually

35 Factors Affecting Bone Development, Growth and Repair  Nutrition  Vitamin D  Needed for calcium absorption  Lack of calcium softens and deforms bones  Vitamin A and C  A is needed for osteoblast and osteoclast activity  Deficiency slows bones development  C is needed for collagen formation  Deficiency leads to slender, fragile bones

36 Factors Affecting Bone Development, Growth and Repair  Hormones  Pituitary gland secretes growth hormone  Stimulates division of cartilage cells  Pituitary dwarfism  Absence of growth hormone  Very short, normal body proportions  Pituitary gigantism  Excess growth hormone  Height over 8 feet  In adults, enlarged hands, feet or jaw

37 Factors Affecting Bone Development, Growth and Repair  (Hormones cont.)  Sex hormones promote bone formation  Abundant during puberty, so long bone growth increases  Also stimulate ossification and eventually stop bone growth  Estrogen is stronger, so females reach maximum height sooner  Physical Stress

38 Factors Affecting Bone Development, Growth and Repair  Physical Stress  Contraction of skeletal muscles cause bone tissue to thicken and strengthen  Hypertrophy  Bones of athletes are stronger and heavier  Lack of exercise cause bone tissue to waste  Atrophy  Fractures can cause shortening of bones  Astronauts experience a 1% loss of bone mass per month in space

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