Human Biology Bones, joints and the skeletal system Classification - - PowerPoint PPT Presentation

Human Biology

Bones, joints and the skeletal system

• Classification and functions of skeletal cartilages.
• Classification and functions of bones.
• Bone structure.
• Bone homeostasis: remodeling and repair.
• An overview of the skeleton.
• Axial skeleton: skull, vertebral column, thoracic cage.
• Appendicular skeleton: pectoral (shoulder) girdle, upper

limb, pelvic (hip) gridle, lower limb.

• Classification and function of joints.
• Fibrous joints.
• Cartilaginous joints.
• Synovial joints.

Classification and functions of skeletal cartilages

Classification of skeletal cartilages Functions of skeletal cartilages

• Hyaline cartilages (articular

cartilages, costal cartilages, respiratory cartilages, nasal cartilages)

• Elastic cartilages (occur in

the external ear and the epiglottis

• Fibrocartilages (e.g. padlike

cartilages (menisci) of the knee and the discs between vertebrae)

• Provide support with flexibility

and resilience

• Withstand both pressure and

tension well

Growth of Cartilage

appositional growth

cartilage-forming cells

secrete new matrix against the external face of the existing cartilage tissue interstitial growth the lacunae-bound chondrocytes divide and secrete new matrix, expanding the cartilage from within

Classification and functions of bones

Classification and functions of bones Functions of bones:

• Support
• Protection
• Movement
• Mineral and growth factor storage
• Blood cell formation
• Triglyceride (fat) storage
• Hormone production (osteocalcin)

Chemical Composition of Bone

Organic Components Inorganic Components

cells (osteogenic cells, osteoblasts,

• steocytes, bone-lining cells, and
• steoclasts)
• steoid , the organic part of the

matrix.

Osteoid includes ground substance (composed of proteoglycans and glycoproteins) collagen fibers, both of which are made and secreted by osteoblasts. consists of inorganic mineral salts, largely calcium phosphates

Bone cells

Structure of Short, Irregular, and Flat Bones

Bone structure

A single osteon

Bone structure

Bone growth

Bone homeostasis: remodeling and repair

Bone deposit Bone resorption

Bone homeostasis: remodeling and repair

• Bone deposit and bone resorption occur at

the surfaces of both the periosteum and the endosteum

• Bone remodeling is coordnated by osteoblast

and osteoclast

• Bone deposit and bone resorption are

balanced in healthy young adults

Bone deposit

Mineralized matrix Calcification front Osteoid seam 10-12 um Unmineralized Produced by osteocytes

Factros trigger calcification:

• Proper concentration of

calcium and phosphate ions

• Presecne of alkaline

phosphatase – enzyme essential for mineralization

Bone resorption

Is accomplished by osteoclasts Osteoclasts :

• Move along a bone surface
• Dig groves
• Break down the bone matrix
• Possess highly folded

membrane (this adaptaion increase area of bone resorption)

• Secrete lysosomal enzymes -

digest organic matrix

• Secrete hydrochloric acid –

convert calcium into soluble form

Hormonal control of bone remodeling

Control of remodeling

Remodeling is affected by many factors:

• Hormones:

 Parathyroid hormone (PTH)—Stimulates osteoclasts

 Calcitonin—Stimulates osteoblasts  Human growth hormone (hGH)—Stimulates cartilage and bone growth  Insulin-like growth factor (IGF)—Stimulates cartilage and bone growth  Sex hormones—Sex-related differences in skeletal growth

• Minerals—Availability of calcium, magnesium, and phosphorus
• Vitamins A, C, and D
• Activity level—Active versus sedentary lifestyle
• Diet

Bone repair

Skull

The orbits

The nasal cavity

The nasal septum and conchae are covered with a mucus- secreting mucosa that moistens and warms the entering air and helps cleanse it of debris. The scroll-shaped conchae increase the turbulence of air flowing through the nasal

• cavity. This swirling forces more of the inhaled air into contact

with the warm, damp mucosa and encourages trapping of airborne particles (dust, pollen, bacteria) in the sticky mucus.

Paranasal sinuses

Small openings connect the sinuses to the nasal cavity and act as “two-way streets”: Air enters the sinuses from the nasal cavity, and mucus formed by the sinus mucosae drains into the nasal cavity. The mucosa of the sinuses also helps to warm and humidify inspired air. The paranasal sinuses lighten the skull and enhance the resonance of the voice.

The hyoid bone

Though not really part of the skull, the hyoid bone lies just inferior to the mandible in the anterior neck, and looks like a miniature version of it. The hyoid bone is unique in that it is the only bone of the body that does not articulate directly with any other bone. Instead, it is anchored by the narrow stylohyoid ligaments to the styloid processes of the temporal bones. Horseshoe-shaped, with a body and two pairs of horns, or cornua, the hyoid bone acts as a movable base for the tongue. Its body and greater horns are attachment points for neck muscles that raise and lower the larynx during swallowing and speech.

Vertebral column

The broad anterior ligament is strongly attached to both the bony vertebrae and the discs. prevents hyperextension of the spine The posterior ligament is narrow and relatively

• weak. It attaches only

to the discs. It resists hyperflexion of the spine Ligamentum flavum connects adjacent vertebrae, Contains elastic connective tissue Is especially strong It stretches as we bend forward and then recoils when we resume an erect posture.

Thoracic cage

Classification and function of joints

Structural classyfication of joints

• Fibrous – dens regular connective tissue holds

together the ends of bones; no joint cavity

• Cartilaginous – pad of cartilage is wedged between

the ends of bones; no joint cavity

• Synovial – ends of bones covered with articular

cartilage; joint cavity separate the articulating bones; enclose by an articular capsule, lined by the synovial membrane; contains synovial fluid

Functional classyfication of joints

• Synarthroses - which are immovable joints
• Amphiarthroses - slightly movable joints
• Diarthroses - freely movable joints

Fibrous joints

Cartilaginous Joints

Synovial joints