Anatomy Exam 2 Skeletal System

Depressions

Cavities and openings -fissure -foramen -fossa -fovea -groove -meatus -notch -sinus -sulcus

Triglyceride (fat) storage

Fat, a source of energy for the body is stored in the bone cavities. Medullary cavity of long bones

What will be the outcome of either type of ossificatinon

The bone is formed and the bone will have spongy bone on the inside and compact bone on the outside

What is the structure of short, irregular, and flat bones

They all share a simple design: they all consist of thin plates of spongy bone covered by compact bone. -These plates are covered inside and outside by connective tissue membranes the periosteum and endosteum -not cylindrical and have no shaft or epiphysis -they contain bone marrow between their trabeculae but have no well defined marrow cavity -Where they form movable joints with their neighbors, hyaline cartilage covers their surfaces

What does oxygen content determine?

Whether a mesenchyme stem cell/ osteogenic precursor (osteoprogenitor) cells differentiate to bone or cartilage

Intramembrous ossification

a bone develops from a fibrous membrane and the bone is called a membrane bone

Epiphyseal plate

a disc of hyaline cartilage that grows during childhood to lengthen the bone.

Projections

bone markings that bulge outward from the surface include heads, trochanters, spines, and others. Each has distinguishing features and functions. In most cases bone projections indicate the stresses created by muscles attached to and pulling on them or are modified surfaces where bones meet and form joints

Osteoclast

bone resorbing cell -giant multinucleate cells located at sites of bone resorption

Support

bones provide a framework that supports the body and cradles its soft organs. -the bones of lower limbs act as pillars to support the body trunk when we stand and the rib cage supports the thoracic walls.

Generally how are bones classified?

classified by their shape as long, short, flat, or irregular

Appendicular skeleton

consists of the bones of the upper and lower limbs and the girdles that attach the limbs to the axial skeleton -bones of the limbs help us move from place to place (locomotion) and manipulate our environment

Compact Bone

every bone has a dense outer layer that looks smooth and solid to the naked eye. -external layer

Axial skeleton

forms the long axis of the body and includes the bones of the -skull -vertebral column -rib cage -these bones protect, support, or carry other body parts

Depressions and openings

fossa, sinuses, foramina, and grooves. -they allow nerves and blood vessels to pass

Collagen fibers

going to be laid down in alternating patterns for strength

Irregular Bones

have complicated shapes that fit none of the classes -vertebrae and hip bones

Osteoblasts

matrix-synthesizing cell responsible for bone growth -actively mitotic -the undermineralized bone matrix they secrete includes collagen and calcium binding proteins that make up the initial unmineralized bone -when the osteoblasts become completely surrounded by the matrix being secreted they become osteocytes

Blood cell formation

most blood cell formation occurs in the red marrow cavities of certain bones. Blood cell production of all blood cells

Material salts

Makes bone hard

Osteocyte

Mature bone cell that monitors and maintains the mineralized bone matrix -As osteocytes die the surrounding matrix is resorbed -act as stress or stain sensors and respond to mechanical stimuli -they communicate this information to the cells responsible for bone remodeling so that bone matrix can be made or degraded as necessary to preserve calcium homeostasis

Spongy Bone

-Internal layer -honeycomb of small needle-like or plate pieces called trabeculae (little beams) -In living bones the open spaces between trabeculae are filled with red or yellow bone marrow

Endochondral ossification

-Replacement of cartilage by bone (cartilage does not change into bone) -responsible for most of the skeletal development, growth of bones both length and width, and fracture repair -hyaline cartilage acts as the catilaginous model -pericardrium covers the hyaline cartilagionus model

Epiphysis

-The bone ends -Broader then the diaphysis -An outer shell of compact bone forms the epiphysis exterior and their interior contains spongy bone -A thin layer of articular (hyaline) cartilage covers the joint surface of each epiphysis, cushioning the opposing bone ends during movement and absorbing stress

Protection

-The fused bones of the skull protect the brain -the vertebrae surround the spinal cord -the rib cage helps protect the vital organs of the thorax

Flat Bones

-Thin, flattened and usually a bit curved -sternum, scapulae, ribs, and skull bones

Structure of a typical long bone

-a shaft, bone ends, and membranes

What are the two divisions of the skeletal system?

-axial skeleton -appendicular skeleton

Formation of bony skeleton

-before week 8 the skeleton of a human embryo is constructed entirely from fibrous membranes and hyaline cartilage -Bone tissue begins to develop at about this time and eventually replaces most of the existing fibrous cartilage structures

What are the three functions of the periosteum

-bone growth and repair -nutrition (nutrient blood vessels) -points of attachment for ligaments

What are the two types of bone textures?

-compact bone -spongy bone

Long Bones

-considerably longer than they are wide -has a shaft plus two ends which are often expanded -all limb bones except the patella and wrist and ankle bones are long bones -elongated shape not for their overall size the three bones in each of your fingers are long bones even though they are small

Short Bones

-cube shaped -wrist and ankle bones -Seasmoid bones are a special type of short bone that forms in a tendon (the patella) -they vary in size and number in different individuals -some seasmoid bones act to alter the direction of pull of a tendon

Membranes of the long bone

-periosteum -nutrient foramina -endosteum

Ossification & Osteogenesis

-process of bone formation -In embryos this process leads o the formation of the bony skeleton -later another form of ossification known as bone growth goes on until early adulthood as the body increases in size -bones are capable of growing thicker throughout life -ossification in adults serves mainly for bone remodeling and repair

Diaphysis

-shaft forms the long axis of the bone -constructed of a relatively thick collar of compact bone that surrounds a central medullary cavity -In adults the medullary cavity contains fat (yellow marrow)

What are the 6 functions of the skeletal system (bones)

-support -protection -facilitate body movement -storage depot for minerals and homeostasis -hematopoiesis -triglyceride storage in yellow marrow of bones

Periosteum

-white double layered membrane -covers the external surface of the entire bone except joint surfaces -the outer fibrous layer of the periosteum is dense irregular connective tissue -The inner osteogenic layer abutting the bone surface consists primarily of primitive stem cell osteogenic cells that give rise to all bone cells except bone destroying cells. contain stem cells that produce bone

Endosteum

-within the bone -covers internal bone surfaces -covers the trabeculae of spongy bone and lines the canals and pass through the compact bone -contains osteogenic cells that can differentiate into other bone cells

What are the 8 projections

projections to which tendons, ligaments, and other connective tissues attach -crest -epicondyle -line -spine -trochanter -trochlea -tubercle -tuberosity

Facilitate body movement

skeletal muscles, which attach to bones by tendons use bones as levers to move the body and its parts. -as a result we can walk, grasp objects, and breathe -the design of the joints determines the types of movements possible

4 Projections

that form joints -condyle -facet -head -ramus

Bone markings

the external surfaces of bones are rarely smooth and featureless they display projections, depressions, and openings. bone markings serve as sites of muscle, ligament, and tendon attachment as joint surfaces or conduits for blood vessels and nerves

Osteon

the structural unit of compact bone tiny weight bearing pillars

Endochondral ossification

within cartilage -a bone develops by replacing hyaline cartilage. the resulting bone is called a cartilage or endochondral bone

Number of bones in adults

206 ossified

Number of bones in children

360 that are not fused yet

Microscopic compact bone

Although compact bone looks solid, a microscope reveals that it is riddled with passageways that serve as conduits for nerves and blood vessels

Osteogenic cells

Stem cells -mitotically active stem cells found in the membranous periosteum and endosteum -in growing bones they are flattened or squamous cells -when stimulated these cells differentiate into osteoblasts or bone lining cells

Epiphyseal line

Between the diaphysis and each epiphysis of an adult long bone is an epiphyseal line, a remnant of the epiphyseal plate

Storage depot for minerals and homeostasis

Bone is a reservoir for minerals most importantly calcium and phosphate. -the stored minerals are released into the bloodstream in their ionic form as needed for distribution to all parts of the body. -mineralized bone matrix stores important growth factors