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Skeletal Tissues. Compact vs. Spongy Compact bone is dense and solid in appearance. Compact bone is dense and solid in appearance. Cancellous, or spongy,

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Presentation on theme: "Skeletal Tissues. Compact vs. Spongy Compact bone is dense and solid in appearance. Compact bone is dense and solid in appearance. Cancellous, or spongy,"— Presentation transcript:

1 Skeletal Tissues

2 Compact vs. Spongy Compact bone is dense and solid in appearance. Compact bone is dense and solid in appearance. Cancellous, or spongy, bone is characterized by open space partially filled by an assemblage of needle-like structures. Cancellous, or spongy, bone is characterized by open space partially filled by an assemblage of needle-like structures.

3 Compact and Spongy Bone

4 Four Bone Types Long bones – extended longitudinal axis and expanded and often uniquely shaped articular ends. Long bones – extended longitudinal axis and expanded and often uniquely shaped articular ends. Examples are the femur and humerus Examples are the femur and humerus Short Bones – cube- or box-shaped structure, which are about as broad as they are long. Short Bones – cube- or box-shaped structure, which are about as broad as they are long. Examples include the wrist (carpals) and ankle (tarsal) bones Examples include the wrist (carpals) and ankle (tarsal) bones

5 Flat bones – generally broad and thin with a flattened and often curved surface. Flat bones – generally broad and thin with a flattened and often curved surface. Examples include some skull bones, scapulae, ribs, and sternum Examples include some skull bones, scapulae, ribs, and sternum Irregular Bones – often clustered in groups and come in various shapes and sizes. Irregular Bones – often clustered in groups and come in various shapes and sizes. Examples include the vertebral bones that form the spine and facial bones Examples include the vertebral bones that form the spine and facial bones

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7 Parts of a Long Bone Diaphysis – main shaftlike portion Diaphysis – main shaftlike portion Epiphyses – both ends of a long bone have a bulbous shape that provides generous space near the joints for stability and muscle attachment. Epiphyses – both ends of a long bone have a bulbous shape that provides generous space near the joints for stability and muscle attachment. Articular Cartilage – thin layer of hyaline cartilage that covers joint epiphyses and acts as a cushion. Articular Cartilage – thin layer of hyaline cartilage that covers joint epiphyses and acts as a cushion.

8 Periosteum – Dense, white fibrous membrane that covers bone except at joint surfaces Periosteum – Dense, white fibrous membrane that covers bone except at joint surfaces Medullary (marrow) cavity – tubelike hollow space in the diaphysis of a long bone. In adults it is filled with fatty yellow marrow. Medullary (marrow) cavity – tubelike hollow space in the diaphysis of a long bone. In adults it is filled with fatty yellow marrow. Endosteum – thin epithelial membrane that lines the medullary cavity of long bones. Endosteum – thin epithelial membrane that lines the medullary cavity of long bones.

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10 Bone (Osseous) Tissue Connective tissue Connective tissue Consists of cells, fibers, and extracellular matrix Consists of cells, fibers, and extracellular matrix Extracellular components are hard and calcified Extracellular components are hard and calcified Matrix is more abundant that the bone cells Matrix is more abundant that the bone cells

11 Composition of Bone Matrix Inorganic Salt are responsible for the hardness of bone. Inorganic Salt are responsible for the hardness of bone. Hydroxyapatite – composed of calcium and phosphate Hydroxyapatite – composed of calcium and phosphate Organic Matrix – composite of collagenous fibers and a mixture of protein and polysaccharides called ground substance. Organic Matrix – composite of collagenous fibers and a mixture of protein and polysaccharides called ground substance.

12 Osteoporosis Age related skeletal disease that is characterized by loss of bone mineral density, increased bone fragility, and susceptibility to fractures Age related skeletal disease that is characterized by loss of bone mineral density, increased bone fragility, and susceptibility to fractures More common in women More common in women May lose 4% - 8% of their bone density on a yearly basis May lose 4% - 8% of their bone density on a yearly basis

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14 Microscopic Structure of Bone Compact bone contains many cylinder-shaped structural units called osteons, or Haversian systems. Compact bone contains many cylinder-shaped structural units called osteons, or Haversian systems. Each osteon surrounds a canal that runs lengthwise through the bone. Each osteon surrounds a canal that runs lengthwise through the bone.

15 Main Structures of the Osteon Lamellae – concentric, cylinder shaped layers of calcified matrix. Lamellae – concentric, cylinder shaped layers of calcified matrix. Lacunae – small spaces containing fluid and bone cells Lacunae – small spaces containing fluid and bone cells Canaliculi – ultrasmall canals radiating in all directions from the lacunae that connects them to each other and the Haversian canal Canaliculi – ultrasmall canals radiating in all directions from the lacunae that connects them to each other and the Haversian canal

16 Haversian canal – Extends lengthwise through the center of each Haversian system; contains blood vessels, lymph vessels and nerves Haversian canal – Extends lengthwise through the center of each Haversian system; contains blood vessels, lymph vessels and nerves Volkmann’s canals – run perpendicular to Haversian canals Volkmann’s canals – run perpendicular to Haversian canals

17 Structure of Compact and Cancellous Bone

18 Section of Flat Bone

19 Cancellous Bone There are no osteons in cancellous bone There are no osteons in cancellous bone Consists of needle-like bony spicules called trabeculae. Consists of needle-like bony spicules called trabeculae. Bone cells are found within the trabaculae Bone cells are found within the trabaculae Nutrients are delivered and wastes removed by diffusion Nutrients are delivered and wastes removed by diffusion

20 Orientation of Trabeculae

21 Types of Bone Cells Osteoblasts – synthesize and secrete a specialized organic matrix called osteoid, that is an important part of the ground substance of bone. (bone forming cells) Osteoblasts – synthesize and secrete a specialized organic matrix called osteoid, that is an important part of the ground substance of bone. (bone forming cells) Osteoclasts – giant multinucleate cells that are responsible for the active erosion of bone minerals. (bone reabsorbing cells) Osteoclasts – giant multinucleate cells that are responsible for the active erosion of bone minerals. (bone reabsorbing cells)

22 Osteocytes – mature, non-dividing osteoblasts that have become surrounded by matrix and now within a lacunae. Osteocytes – mature, non-dividing osteoblasts that have become surrounded by matrix and now within a lacunae.

23 Osteoblasts and Osteocytes

24 Osteoclast

25 Bone Marrow Soft, diffuse connective tissue called myeloid tissue. Soft, diffuse connective tissue called myeloid tissue. Site of blood cell production Site of blood cell production Found in medullary cavities of certain long bones and in the spaces of some spongy bones. Found in medullary cavities of certain long bones and in the spaces of some spongy bones.

26 Red Marrow & Yellow Marrow In a child’s body, virtually all of the bones contain red marrow. In a child’s body, virtually all of the bones contain red marrow. Red marrow produces red blood cells. Red marrow produces red blood cells. As an individual ages red marrow is replaced by yellow marrow. As an individual ages red marrow is replaced by yellow marrow. Yellow marrow has become saturated with fat and is no longer active in blood cell production. Yellow marrow has become saturated with fat and is no longer active in blood cell production.

27 Active Marrow in Adults

28 Functions of Bone Support – supporting framework of body Support – supporting framework of body Protection – protect delicate structures such as the brain Protection – protect delicate structures such as the brain Movement – joints act as levers and allow movement in conjuction with muscular system Movement – joints act as levers and allow movement in conjuction with muscular system Mineral Storage – major reservoir for calcium, phosphorus, and certain other minerals Hematopoiesis – blood cell formation

29 Regulation of Blood Calcium Levels 98% of body calcium is stored in bone 98% of body calcium is stored in bone Osteoblasts remove calcium from blood Osteoblasts remove calcium from blood Osteoclasts break down bone and calcium levels in the blood increases Osteoclasts break down bone and calcium levels in the blood increases Calcium is important for normal blood clotting, nerve impulses, and muscle contraction Calcium is important for normal blood clotting, nerve impulses, and muscle contraction

30 Calcium in the Body Calcium that is consumed is absorbed through the intestines Calcium that is consumed is absorbed through the intestines Calcium is stored and released from bone tissue Calcium is stored and released from bone tissue The kidneys eliminate extra calcium and absorb calcium from urine if blood calcium levels get too low. The kidneys eliminate extra calcium and absorb calcium from urine if blood calcium levels get too low.

31 Parathyroid Hormone When calcium levels fall below their “set point,” osteoclasts are stimulated to increase the rate of bone matrix breakdown. When calcium levels fall below their “set point,” osteoclasts are stimulated to increase the rate of bone matrix breakdown. Calcium is released into the blood until the level returns to normal. Calcium is released into the blood until the level returns to normal.

32 Vitamin D (Calcitriol) Acts to increase blood calcium levels Acts to increase blood calcium levels Facilitates the absorption of calcium in the small intestines Facilitates the absorption of calcium in the small intestines

33 Calcitonin Functions to reduce blood calcium levels Functions to reduce blood calcium levels Enhances excretion of calcium in urine Enhances excretion of calcium in urine Inhibits osteoclasts Inhibits osteoclasts

34 Calcium Deprivation

35 Development of Bone Before birth, the skeleton consists of cartilage and fibrous structures shaped like bones. Before birth, the skeleton consists of cartilage and fibrous structures shaped like bones. Cartilage is replaced with calcified bone matrix Cartilage is replaced with calcified bone matrix The combined action of osteoblast and osteoclasts to make bone is known as osteogenesis The combined action of osteoblast and osteoclasts to make bone is known as osteogenesis

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37 Intramembranous Ossification Takes place within a connective tissue membrane Takes place within a connective tissue membrane

38 Endochondral Ossification Bone forms from cartilage models Bone forms from cartilage models Forms from the center to the ends Forms from the center to the ends

39 Endochondral Ossification

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44 Epiphyseal Fracture

45 Bone Growth and Resorption Bone growth is from the combined action of osteoclasts and osteoblasts Bone growth is from the combined action of osteoclasts and osteoblasts Osteoclasts break down bone to enlarge the diameter of the medullary cavity. Osteoclasts break down bone to enlarge the diameter of the medullary cavity. Osteoblasts from the periosteum build new bone around the outside of the bone Osteoblasts from the periosteum build new bone around the outside of the bone

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47 Bone Fracture Repair


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