lab9: skeletal

• The skeletal system consists of the framework of bones and their cartilages, joints and ligaments.
• The adult human skeleton contains 206 named bones.
• These bones are further divided into the axial skeleton (80 bones) and the appendicular skeleton (126 bones).
• The axial skeleton consists of bones that form the long axis of the body – skull, vertebral column and thoracic cage.
• The appendicular skeleton consists of the bones of the upper and lower limbs, plus the bones forming the girdles that connect the limbs to the axial skeleton.
• short bones are roughly cube-shaped found in wrists and ankles
• Most bones of the body can be classified into five main types based on their shape: long, short, flat, irregular, and sesamoid.
• Long bones are longer than they are wide and include the bones of the limbs such as the humerus, radius, and ulna; the femur, tibia, and fibula; and the phalanges.
• Long bones are slightly curved for strength, so that the stress of the body’s weight is evenly distributed at several points.
• Compact bone occurs at the surface of long bones, particularly in the diaphysis or shaft region.
• flat bones are thinner than they are long. Found in skull bones, scapula, sternum, and ribs
• The dilated extremities or epiphyses of the bone consist of spongy bone covered by a thin layer of compact bone.
• Irregular bones: bones that are neither long, short, or flat. They have complicated shapes. Found in hip bones and vertebrae
• Sesamoid bones: small irregular bones embedded within tendons to reduce friction between muscle and bone during movement. Found in patella and tendons of hands and feet
• The external surfaces of bones are rarely smooth, but instead have characteristic surface markings.
• Bones display projections or outgrowths that either help form joints or serve as sites of ligament and tendon attachment.
• Bones also have depressions which form joints and openings which allow for the passage of nerves and blood vessels.
• Process: any body prominence
• Tubercle: rounded projection on a bone
• Tuberosity: large rounded projection; may be roughened; attachment of muscles/ligaments
• Trochanter: very large,blunt irregular shaped process/projection
• Condyle: rounded articular projection/ helps from joints
• Epicondyle: raised area on or above a condyle
• facet: smooth, nearly flat articular surface (for rib attachment to vertebrae)
• Crest: narrow bridge of bone; usually prominent
• Head: bony expansion carried on a narrow neck
• Foramen: round or oval opening through a bone
• Meatus: canal-like passageway
• fossa:shallow, basin-like depression in bone (filled with air & lined with mucus membrane)
• The axial skeleton consists of bones which form the long axis of the skeleton: the skull, auditory ossicles (middle ear bones – malleus, incus, stapes), hyoid bone, the vertebral column, the sternum and the ribs.
• The skeleton of the developing embryo consists of fibrous connective tissue membranes and hyaline cartilage shaped like future bones.
• Gradually, ossification occurs – bone tissue starts to develop about 8 weeks after conception.
• This process of ossification occurs in the embryonic skull by a process called intramembranous ossification.
• At birth, areas of fibrous connective tissue called fontanels, still exist between the cranial bones.
• These fontanels, also known as the “soft spots” of a baby’s skull, provide some flexibility to the fetal skull.
• The fontanels allow the skull to compress as it passes through the birth canal and permit rapid growth of the brain during infancy.
• Ossification is usually complete by two years of age and the fontanels become sutures.
• The adult skull is formed by blank and blank bones, 22 in total.
• The cranial bones enclose and protect the brain and are a site for the attachment of head and neck muscles.
• Sutures are immoveable joints in the adult skull and four major ones will be identified – coronal, sagittal, squamous, and lambdoid sutures.