Bones and Skeletal Tissue

Osteology

the study of bones

Applications of osteology

zoology, forensic science, physical anthropology, archeology, demography, diet, genetics & disease.

Number of bones in the adult human body

206 bones with some variation.

Sutural (wormian) bones

extra bones within sutures of skull

sutures

an immovable, rigid joint that connects the different flat bones of the skull; think of the medical term for stitches

Bone and skeletal tissue could be markers for

disease such as down syndrome

sesamoid bones

bones that develop from tendons (patella)

Bones are considered _______ containing __________

organs, skeletal tissue

skeletal system contains

bones, cartilage, ligaments, other connective tissue

The skeletal system is

dynamic/interactive; it is not static, but grows and interact with other body systems.

Functions of skeletal system

support, protection (skull, rib cage) for visceral organs, body movement (levers & pivots: bones & joints), hemopoiesis (RBC, WBC, platelets), mineral storage.

Calcium

aids with muscle contraction, blood clotting, nervous system (signaling)

Phosphorus

nucleic acids, ATP

Mesenchyme

first connective tissue to emerge, gives origin to all other tissues

Type of tissue present in skeletal system

Supporting connective tissue: cartilage and bone

Cartilage

Hyaline, fibrocartilage, elastic

Hyaline Cartilage

The most common in the body, supports soft tissue, weakest of cartilages, fetal skeleton (turns into bone over time), articular cartilage, nose, trachea, ribs-sternum

Fibrocartilage

Contains many dense collagen fibers in between, found in intervertebral discs, pubic symphysis, meniscus. Strongest kind of cartilage in humans.

Elastic Cartilage

Contains numerous elastic fibers in matrix, ear, epiglottis, very flexible.

Intramembranous ossification*

forms bones straight from mesenchyme, without cartilage intermediate.*

Endochondral ossification

first starts with mesenchyme to create temporary hyaline cartilage, then forms bones.

Bone connective tissue

• Stronger, denser than cartilage.

• Collagenous fibers give flexibility to bone; calcium phosphate in the matrix gives the bone its hardness.

• 1/3 organic components (fibers), the remaining inorganic (Ca phosphate)

Periosteum

Tougher, outer connective tissue covering the bone, one that grows in response to physical activity.

Endosteum

Delicate inner membrane lining the internal cavities and bone marrow spaces.

Medullary Cavity

Cavity in the middle of the bone.

Compact bone tissue

• organized into osteons

• perorating canals (Volkmann’s canals)

• perforating fibers (Sharpey’s fibers)

• has concentric lamellae around central canal

• Collagen bundles that hold periosteum to bone matrix

Spongy bone

• no osteons

• built from trabeculae: parallel lamellae

• spaces between trabeculae with yellow or red bone marrow

• long bones in epiphysis (tip)

• Flat bones: sandwiched (dipole)

• Distributes stress, reduces weight

Bone Matrix

Contains organic and inorganic cells; collagen fibers and calcium phosphate

Collagenous fibers

Gives flexability to bone

Calcium phosphate

gives bone its hardness

Osteoblasts

• building more bone

• derived from mesenchyme (osteogenic cells)

• secrete collagen & matrix

• secretes hormones that regulate sugar metabolism

Osteogenic Cells

stem cells that develop from mesenchyme and give rise to other bone cells

Osteoclasts

• Bone dissolving macrophages that. Secretes acid to dissolve mineral portion of bone (osteolysis)

• modified monocytes (WBC), large, multinuclear

• bone reabsorbing cells

• release lysosomal enzymes

Osteolysis

Breaking down bones.

Osteocytes

• former osteoblasts that have become embedded in the matrix they deposited

• mature cells formed when matrix surrounds osteoblasts

• trapped in lacunae

Long Bone

More common

Long bones

levers

Long bones

upper/lower extremities

Short bones

about as long as wide

Short bones

articulate and distribute forces

Short bones

Carpals

Short bones

Tarsals

Short bones

Sesamoid bones

Flat bones

skull

Flat bones

ribs

Flat bones

scapula

Flat bones

produce RBC

Flat bones

extensive surface for muscle attatchment

Flat bones

Hemopoiesis in adults

Irregular bones

complex shapes

Irregular bones

Vertebrates

Irregular bones

Coxae

Irregular bones

Some in skull

Structure of a flat bone

shield-like plates that protect delicate organs (i.e. the brain, heart) and form broad surfaces for muscle attachment

Structure of a flat bone

Sandwich-like construction with inner and outer tables; spongy bone (diploe) containing trabeculae and compact bone.

Spine

Sharp projection

Tubercle/ Tuberosity

Round projection

Articulation

Condyle

Articulation

Facet

Articulation

Head

Projection

Tuberosity

Projection

Crest

Projection

Trochanter

Projection

Line

Projection

Tubercle

Projection

Epicondyle

Projection

Spine

Projection

Process

Depression/Cavities

Alveolus

Depression/Cavities

Fossa

Depression/Cavities

Canal

Depression/Cavities

Fissure

Depression/Cavities

Foramen

Depression/Cavities

Sinus

Depression/Cavities

Groove

Depression/Cavities

Meatus

Red bone marrow

Produces RBC, found in flat bones, proximal epiphysis of humerus, femur

Red bone marrow in children

• found in spongy bone and medullary cavity

• most bones

Red bone marrow in adults

• red bone marrow turns into fatty tissue: yellow bone marrow (makes RBC in emergencies)

Ossification

Begins by 4th week of prenatal development, some until early 20s

Endochondral ossification

• Develops from models of hyaline cartilage

• Most skeletal develops this way

Intramembrane ossification

• Develops from mesenchyme, not from cartilage

• Some bones of skull, clavicles, sesamoid bones

Diametric growth

• Occurs at the periosteum of the diaphysis

• High osteoblast activity in the periosteum

• High osteoclast activity in the endosteum

Vertical growth

• Epiphyseal plate (growth plate)

• Genetically determined

• Epiphyseal line when growth stops

Fontanelles “soft spots”

• 6 large membranous areas of skull

• Allow changes during childbirth

• Allow rapid growth of brain

• Ossification complete by 24 months

Ligament

bone to bone; prevent movement

Tendon

bone to muscle; promotes movement

Osteoporosis

• Osteoclast activity > than Osteoblast activity

• Loss of total bone mass, including matrix

Risk Factors of Osteoporosis

• Diet & lifestyle

• Age

• Sex: women have less bone mass, lose fast and earlier

• Postmenopausal women at greater risk because lower level of estrogen.

Detoxification

The skeleton’s ability to absorb heavy metals and thus keeping them from harming the surrounding tissues

Flat bones

Thin, often curved