Bones and Skeletal Tissues Chapter 6 Bones and Skeletal Tissues Part A

Objectives List the functions of the skeletal system List with examples the types of bones Label parts of a typical bone List the gross and microscopic structure of osseous tissue; match and select from a list with 100% accuracy List and describe the steps in endochondral and intramembranous ossification Describe in your own words bone development and growth List the hormones and inorganic elements that regulate homeostasis of the skeletal system. Match and select from a given list with 100% accuracy and be able to write short answers to critical thinking questions Name and identify homeostatic imbalances of the skeletal system; match and select from a given list with 100% accuracy List and describe the different types of fractures List and name/label bone markings and bone of the axial and appendicular skeleton

Skeletal Cartilage Contains: No blood vessels No nerves Surrounded by an outer layer called the perichondrium: Made of dense irregular connective tissue Resists outward expansion upon compression Vascularized, nutrients diffuse thru matrix to cartilage cells Three types of skeletal cartilage: Hyaline Elastic Fibrocartilage

Hyaline Cartilage Most abundant skeletal cartilage Hyaline cartilages include: Articular cartilage: Covers the ends of long bones Costal cartilage: Connects the ribs to the sternum Respiratory: Makes up the larynx (voicebox) Reinforces other air passages Nasal: Supports the external nose

Similar to hyaline cartilage Contains mor elastic fibers Elastic Cartilage Similar to hyaline cartilage Contains mor elastic fibers Better able to stand up to repeated bending Found in only two locations: External ear Epiglottis

Highly compressible & have great tensile strength Fibrocartilages Highly compressible & have great tensile strength Contains collagen fibers Found in the: Knee joint Intervertebral discs Pubic symphysis

Bones and Cartilages of the Human Body Figure 6.1

Growth & Calcification of Cartilage Two types growth: Appositional: Inward growth (growth from outside) By perichondrial fibroblasts Interstitial: Outward growth (growth from inside) By lacunae-bound dividing chondrocytes

Growth & Calcification of Cartilage Cartilage growth stops during: Adolescence (when the skeleton stops growing) Calcified (hardened) cartilage: Is not bone Occurs under certain condition during: Normal bone growth (in youth) Old age Due to: Deposition of Ca salts in the matrix

Function of Bones Support : Protection: Movement: Mineral storage: Framework; supports the body and cradles soft organs Protection: Protective case (brain, spinal cord, and vital organs) Movement: Provide levers for muscles Mineral storage: Reservoir for minerals, especially Ca and P Blood cell formation: Hematopoiesis occurs in marrow cavities of certain bones

Classification of Bones (skeleton level) All bones (206) of the human skeleton are divided into two groups: Axial skeleton, comprises the bones of the: skull vertebral column rib cage Appendicular skeleton, comprises the bones of the: upper & lower limbs Shoulder & hip

Classification of Bones: Bone Textures Bones are composed of two main types of osseous tissue: Compact bone Dense, homogeneous, smooth outer layer Spongy bone: Honeycomb of trabeculae (bars) Trabecular space is filled with red or yellow bone marrow

Classification of Bones: By Shape Bones are classified according to their gross anatomy (shape) into: Long bones Short bones Flat bones Irregular bones

Long Bones Long bones: longer than wider Predominantly compact bones Examples: Humerus Femur Figure 6.2a

Short Bones Short bones: Cube-shaped bones of the wrist & ankle Predominantly spongy bones Examples: Carpals & tarsals Some form in tendons: Called sesamoid bones Example: Patella Figure 6.2b

Flat Bones Flat bones: Thin, flattened, and a bit curved Two layers of compact bones sandwiching a spongy bone Examples: Sternum Most of skull bones Figure 6.2c

Irregular Bones Irregular bones: Bones with complicated shapes Do not fit other shapes Examples: Vertebrae Hip bones Figure 6.2d

Break Slide Biol2401.33248 (Alief) Mon, Feb 11, 2012

Structure of Long Bone Long bones consist of: Diaphysis A diaphysis and An epiphysis Diaphysis Tubular shaft that forms the axis of long bones Constructed of: A thick collar of compact bone Central medullary cavity (marrow cavity) that contains: Yellow bone marrow (fat) in adults Red bone marrow in young

Structure of Long Bone Epiphyses Expanded ends of long bones Exterior is compact bone, Interior is spongy bone Joint surface is covered with articular (hyaline) cartilage Epiphyseal line (adults) or plate (children) separates the diaphysis from the epiphyses

Structure of Long Bone Figure 6.3

Structure of Long Bone Figure 6.3a

Structure of Long Bone Figure 6.3c

Structure of Long Bone Figure 6.3b

Bone Membranes Periosteum: Double-layered protective membrane constructed of: An outer fibrous layer (dense irregular c.t.) An inner osteogenic layer (at bone surface) composed primarily of: Osteoblasts: bone-matrix forming cells Osteoclasts: giant cells that resorb (break) bone matrix Osteogenic cells: stem cells that give rise to osteoblasts Richly supplied with nerve fibers, blood, and lymphatic vessels Contains nutrient foramina (pores) for blood & lymph vessels & nerve fibers to enter the bone tissue Secured to underlying bone by Sharpey’s fibers

Bone Membranes Endosteum: Delicate deeper membrane covering internal surfaces of bone: Covers trabeculae of spongy bones Lines canals of compact bones Also contains: Osteogenic cells Osteoblasts Osteoclasts

Structure of Short, Irregular, and Flat Bones Constructed of: Thin outside plates of compact bone covered by the periosteum Spongy bone (diploe) on the inside covered by the endosteum Have no diaphysis or epiphyses Contain bone marrow between the trabeculae

Hematopoietic Tissue (Red Marrow) Location Typically found: Within trabecular cavities of spongy bones of long bones In spongy bone (diploe) of flat bones In infants found in: The medullary cavity All areas of spongy bone In adult found in: The heads of the femur and humerus The spongy bone regions of flat bones e.g. sternum Some irregular bones e.g. hip bone Yellow marrow can revert to red marrow in severe anemia

Microscopic Structure of Bone: Compact Bone Four types of cells populate the bone tissue: Osteogenic (osteoprogenitor): bone stem cells found in the membranous endosteum and periosteum Osteoblasts: bone-forming cells differentiating from osteogenic cells Osteocytes: mature bone cells Osteoclasts: bone-breaking cells Lacunae: Small cavities in bone that contain osteocytes Canaliculi: Hairlike canals Connect lacunae to each other & to the central canal

Microscopic Structure of Bone: Compact Bone Haversian system, or osteon: Is the structural unit of a compact bone An elongated cylinder parallel to the long axis of the bone Made of concentric hollow tubes of matrix called lamellae Central or Haversian canal: A channel running thru the core of each osteon Contains nerves and blood vessels Perforating(Volkmann’s) canals: Channels perpendicular to the long axis of the bone Connect periosteal blood & nerve supply to those in the central canal & medullary cavity

Microscopic Structure of Bone: Compact Bone Figure 6.6a, b

Microscopic Structure of Bone: Compact Bone Figure 6.6a

Microscopic Structure of Bone: Compact Bone Figure 6.6b

Microscopic Structure of Bone: Compact Bone Figure 6.6c

Matrix Component of Bone: Osteoid (Organic): Unmineralized bone matrix Constitute 1/3 of matrix Include: Ground substance (proteoglycans & glycoproteins) Collagen fibers Hydroxyapatites or mineral salts (Inorganic): Constitute 65% of bone by mass Mainly calcium phosphates Responsible for: Bone hardness Resistance to compression