HESS 510 PPT Series 1B Foundations of Structural Kinesiology

Body Regions (skeletal mass) The skeletal mass is subdivided into two basic components: The Axial and the Appendicular Skeleton Appendicular Upper limbs Lower limbs Axial Cephalic (head) Cervical (neck) Trunk

Osteology (Bone the study of) Adult skeleton has approximately 206 bones (FYI). Exact number of bones as well as their specific features occasionally varies from person to person Axial skeleton Contains 80 bones (FYI) Appendicular skeleton Contains 126 bones (FYI)

Skeletal Functions Protection – Which systems and organs are protected by the skeletal mass? Posture – How does the skeletal mass promote stability and posture? Movement – How does the skeletal mass promote movement (muscles and levers)? Storage of minerals (calcium and phosphorus) Hemopoiesis –blood cell production… see next slide

Skeletal Functions Hemopoiesis – FYI not on test for discussion only

Types of Bones Bones vary in shape and size and are classified into five major categories: Long bones Short bones Flat bones Irregular bones Sesamoid bones

Types of Bones – Long Bones Composed of a long cylindrical shaft with relatively wide, protruding ends. The shaft contains the medullary cavity Examples pictured - Femur, Radius, Ulna

Types of Bones – Short Bones Small cube-shaped, solid bones that usually have a proportionally large articular surface in order to articulate with more than one bone Examples Pictured– Capitate (carpal bone) and Talus (tarsal bone)

Types of Bones – Flat Bones Usually have a curved surface and vary from thick, (where tendons attach), to very thin. Flat bones generally provide protection. Examples Pictured – Scapula, Sternum = (manubrium, body, xiphoid process)

Types of Bones – Irregular Bones Irregular shaped bones serve a variety of purposes Irregular bones are found throughout the entire body. Examples Pictured: Sphenoid (found in craniofacial skeleton, and a thoracic vertebra.

Types of Bones -Sesamoid Bones Small bones embedded within tendon of a musculotendinous unit that provide protection and improve mechanical advantage (more discussion on mechanical advantage p.72, text) of musculotendinous units. Examples Pictured – Patella, Sesamoid of Great Toe

Typical Bony Features - Terms Diaphysis – (dia = through; physis = something the grows / develops) Long cylindrical shaft Cortex – (word origin = bark, shell, husk) Hard, dense and compact bone forming walls of the diaphysis Periosteum – (peri = about or around; osteum = bone) Dense, fibrous membrane covering the outer surface of the diaphysis

Typical Bony Features - Terms Endosteum – (Endo = within) Fibrous membrane that lines the inside of the cortex Medullary (word origin = marrow, pith) cavity Lies between the walls of the diaphysis Contains yellow or fatty marrow

Typical Bony Features - Terms Epiphysis (Epi= at or near; physis = something that grows / develops) Appears at the ends of long bones Formed from cancellous (word origin = lattice) bone. Cancellous bone is also called spongy or trabecular (word origin = little beam) bone Epiphyseal plate (also called growth plate) Thin cartilage plate that separates the diaphysis and the epiphysis

Typical Bony Features - Terms Articular (word origin = pertaining to joints) cartilage (word origin = gristle) Covers the epiphysis to provide a cushioning effect and reduces friction

Bone Growth Endochondral bones (endo = within) Develop from hyaline (word origin = glass) cartilage. Hyaline cartilage is found between many bone articulations (hip/knee) Hyaline cartilage masses grow rapidly into structures as humans develop from an embryo.

Bone Growth Grow rapidly into structures shaped similar to the bones that they will eventually become Growth continues, and cartilage gradually undergoes significant change to develop into long bone

Bone Growth Longitudinal growth continues as long as the epiphyseal plates are open Around adolescence, plates begin closing and disappear Note growth in both vertical and longitudinal directions. As bone continues to develop the medullary cavity forms and bone diameter increases with an increase in the diaphysis.

Bone Growth Most close by age 18, but some may be open until age 25 Growth in diameter continues throughout life as the internal layer of periosteum builds concentric layers on older layers. Simultaneously, bone around the medullary cavity is resorbed so that the diameter is continually increased

Bone Growth New bone is formed by specialized cells called osteoblasts (blast = bud, sprout) Cells that remove (resorb) old bone tissue are called osteoclasts (clast = to cut) Activity of both permit bone remodeling

Bone Properties Composed of calcium carbonate, calcium phosphate, collagen, and water 60–70% of bone weight = Minerals: Calcium carbonate and calcium phosphate 25–30% of bone weight = Water Collagen (word origin: colla = glue; -gen = that which produces) provides some flexibility and strength in resisting tension Aging causes progressive loss of collagen and increases bone brittleness

Bone Properties Most outer bone is cortical; cancellous bone is underneath Cortical bone - 5%–30% of volume is porous (low porosity) Cancellous bone (trabecular )- Spongy with 30 to 90% of its volume being porus Cortical bone is stiffer and can withstand greater compression stress, but less strain, than cancellous bone Cancellous bone is spongier and can undergo greater strain (deformation) before fracturing

Bone Properties Wolff’s law Bone size and shape are influenced by the direction and magnitude of forces that are habitually applied to them Bones reshape themselves based on the stresses placed upon them Bone mass increases over time with increased stress

Bone Markings Bone Markings may be defined in two major categories: Processes (including elevations and projections)which either form joints or serve as a point of attachment for muscles, tendons, or ligaments. Cavities (word origin = hollow) which include openings and groves that contain tendons, vessels, nerves, and spaces for other structures. Study all terms in Table 1.4, p. 15 End PPT Series 1B