Bone Terms, Skeletal Overview & Skull Bones

3 types of cartilages

hyaline cartilage, fibrocartilage, elastic cartilage

hyaline cartilage description

not too tough or not too bendy (happy medium)

hyaline cartilage location

lining the articular ends of bones in movable joints (knee, hip, shoulder), within the respiratory tract (trachea, larynx, bronchi), in the nose, and connecting the ribs to the sternum (costal cartilage)

fibro cartilage description

very tough

fibro cartilage location

intervertebral discs, knee menisci, pubic symphysis, shoulder/hip labrum, wrist (TFCC), and at the insertion points of tendons and ligaments into bone

elastic cartilage description

bendy

elastic cartilage location

external ear (pinna), the epiglottis, and the Eustachian (auditory) tube

bone functions

support, protections, levers for muscle action, minerval storage, blood cell formation, triglyceride energy storage

2 divisions of skeleton

axial skeleton (protection/support), appendicular skeleton(movement)

axial skeleton

skull, vertebral columns, thoracic cage

bones that lie around the body’s center of gravity

appendicular skeleton

limbs, girdles (pectoral and pelvic)

involved in locomotion and manipulation of the environment

classification of bones by shape

long bones, short bones, flat bones, irregular (anything that doesn’t fall in those categories

2 categories of bone marking

1. projections

2. depressions/opening

projections bone markings

stuff that pops out of the bone, sites of muscle and ligament attachment, helps form joints

depressions/openings bone markings

indents or holes in bones, passageways for blood vessels and nerves

process

any prominence on bone

tuberosity

a large raised roughened projection on bone for the attachment of muscles

crest

projection, narrow ridge on bone, very prominent

trochanter

projection, only found on femur, large blunt irregularly shaped things that stick out

line

projection, a narrow ridge of bone less prominent than crest

tubercle

projection, rounded process that stick out of bone, smaller than tuberosity

spine

projection, sharp slender often pointed

condyle

projection, knuckle like

epicondyle

projection, on or above a condyle

ramus

projection, branch like structure on a bone or arm like bar of bone

cornu

projection, horn shaped

head

projection, rounded process or expansion supported by a constricted/narrowed neck

facet

projection, small smooth/nearly flat surface for articulation

groove

depression/opening, furrow

fissure

depression/opening, narrow slit like opening

foramen

depression/opening, round oval opening (hole) through a bone that allows passage of nerves and or blood vessels

canal

depression/opening, a narrow tube, channel, or passageway through a bone

notch

depression/opening, indentation at the edge of a structure

meatus

depression/opening, canal or tube like passageway through a bone

fossa

depression/opening, shallow basin like depression in a bone often serves as an articular surface

fovea

depression/opening, a deep pit or depression in a bone

sulcus

depression/opening, narrow groove or furrow in a bone

alveolus

depression/opening, deep pit or socket in the mandible or maxillae for a tooth

sinus

depression/opening, a cavity or hollow space in certain skull bones filled with air and lined with mucous membrane

4 in the skull=frontal ethmoidal sphenoidal maxillary sinuses, lighten the skill and help with voice resonance

squama

a flat portion/area on a bone

ala

a wing like portion of bone

visceral skeleton

skeletal elements/bones derived from the embryonic gill arches; not directly part of the main skeleton. Include the ear ossicles (malleus, incus, stapes), the hyoid bone, and portions of the larynx

conchae

a lateral (scroll-like) fold of bone in the nasal cavity that creates a more efficient circulation of inhaled air (increases air flow) by increasing surface area

suture

a line remaining after 2 bones have joined together and fused; seen between skull bones

fontanelle

spaces covered by tough membranes (connective tissue) between the bones of a fetus/infant’s skull; “soft spots” on a baby’s skull where bones haven’t fused. Allow for easier childbirth and brain growth.

2 types of bone texture

compact bone, spongy (cancellous) bone

compact bone

Dense outer layer; looks smooth & solid to naked eye

spongy, cancellous, bone

Inner layer; lots of open space…honeycomb of trabeculae

structure of a long bone, diaphysis

main part of the bone, shaft that forms long axis of the bone; walls composed of thick layer of compact bone; contains the medullary cavity

structure of a long bone, epiphysis

rounded end of the bone, proximal and distal; outer layer of compact bone with internal spongy bone; articular cartilage covers surface (layer of hyaline cartilage where joints form)

structure of a long bone, epiphyseal line

The remnant of the epiphyseal (growth) plate between the diaphysis and epiphysis at each end; marks where bone growth in length occurred

structure of a long bone, medullary cavity

hollow space within the diaphysis; contains yellow bone marrow for fat storage (adipose)

structure of a long bone, periosteum

membrane covering the outer surface of the bone; composed of dense irregular connective tissue; contain bone stem cells

microscopic anatomy of compact bone, osteon/haversian system

circular structural units of compact bone; comprised of multiple concentric layers of calcified matrix (lamellae) surrounding a central canal

microscopic anatomy of compact bone, central/haversian canal

opening in center of each osteon; passageway for blood vessels and nerves

microscopic anatomy of compact bone, lamellae

rings/layers of calcified matrix around the central canal= concentric lamellae; interstitial lamellae= located between osteons; remnants of old osteons

microscopic anatomy of compact bone, osteocytes

mature bone cells; reside in lacunae

microscopic anatomy of compact bone, lacuna

open spaces in matrix that house osteocytes

microscopic anatomy of compact bone, canaliculi

small canals through matrix; appear as “cracks”; contain cytoplasmic extensions of osteocytes; connect lacuna and osteocytes to each other

microscopic anatomy of compact bone, perforating (volkmann’s) canals

passageways that run perpendicular to the central canal; connect blood and nerve supply throughout the bone

Ossification

process of bone formation and development; most bones of the skeleton form by endochondral ossification

endochondral ossification

uses hyaline cartilage as a model or template; this is also how bones grow in length

Epiphyseal (growth) plate

region of a long bone between the diaphysis and epiphyses composed of hyaline cartilage; only present during childhood and adolescence; allows bone to grow in length; has 5 functional zones (from epiphysis to diaphysis)

Resting (quiescent) zone

Small, inactive cartilage cells scattered randomly.

Chondrocytes (inactive)

Anchors the epiphyseal plate to the epiphysis and stores cells for future growth.

Proliferation (growth) zone

Cartilage cells rapidly divide and form columns.

Chondrocytes undergoing mitosis

Lengthens the bone by increasing the number of cartilage cells.

Hypertrophic zone

Older cartilage cells enlarge and mature.

Enlarged chondrocytes

Prepares cartilage for calcification and eventual bone replacement.

Calcification zone

Cartilage matrix hardens; chondrocytes die.
Dead chondrocytes in calcified cartilage
Stops cartilage growth and allows blood vessels to invade.

Ossification (osteogenic) zone

New bone tissue forms on calcified cartilage.
Osteoblasts (forming bone)
Replaces cartilage with bone, contributing to bone lengthening.

Order of epiphyseal (growth) plate

Resting (quiescent) zone Proliferation (growth) zone Hypertrophic zone Calcification zone Ossification (osteogenic) zone

Chemical Composition of Bone

organic and inorganic

organic chemical composition of bone

bone cells & organic part of the matrix (ground substance & collagen fibers); provides bone with flexibility

inorganic chemical composition of bone

mineral salts in the matrix (e.g., calcium); provides bone with characteristic hardness

frontal bone

anterior cranium; articulates posteriorly with parietal bones @ coronal suture; contains sinuses

frontal bone (squama/squamous part)

(scale-like)- large, rounded superior part of bone above orbits

frontal bone (glabella part)

(hairless, smooth)- smooth area between the orbits

frontal bone (supraorbital margin part)

thick, superior border of the eye socket

frontal bone (supraorbital foreamen/notch part)

small hole/indentation in supraorbital margin

parietal bone

(wall)- curved, rectangular bones behind frontal bone; form most of superior and lateral portion of skull; join at midline @ sagittal suture

occipital bone

forms most of skull’s posterior wall and base; has large hole in its base; articulates anteriorly with parietal bones and temporal bones; also joins with sphenoid bone in cranial floor

occipital bone (External Occipital Protuberance)

external median protrusion; knoblike; can feel it just below most bulging part of skull

occipital bone (Superior Nuchal Line)

inconspicuous ridge spanning laterally from the externaloccipital protuberance

occipital bone (Infeorior Nuchal Line)

inconspicuous ridge spanning laterally; located below superior nuchal line

occipital bone (foramen magnum)

large hole in base of bone; flanked laterally by condyles; passageway for spinal cord to exit skull

occipital bone (Occipital Condyles)

rocker-like projections; articulate with first vertebrae; permits nodding of head

occipital bone (Condylar Canal)

opening posterior to condyle; seen on inferior view of bone

occipital bone (Hypoglossal Canal)

passageway running through condyle; can be seen from inside foramen magnum

Wormian/Sutural Bones

tiny, irregular shaped bones/bone clusters that appear within sutures; most often seen at lambdoidal suture; unimportant, # varies, not all skulls have them

temporal bone

forms lateral wall of skull and part of cranial floor; complicated shape; has several processes & foramina

temporal bone (Zygomatic Process)

long projection that articulates with zygomatic bone anteriorly (forms part of zygomatic arch!)

temporal bone (styloid Process)

(projection like a writing stylus/pen)- sharp, needle-like projection pointing inferiorly; located below external acoustic meatus

temporal bone (mastoid Process)

(breast-shaped)- thick, rounded projection on inferior, posterior part of bone; can feel it- lump posterior to your ear

temporal bone (Squamous Portion/Part)

(thin & flat like a fish’s scale): flaring, flat part of bone; joins parietal bone @ squamous suture

temporal bone (Petrous Portion)

(stone, rock)- “rocky” part of bone that contributes to cranial base; mini mountain ridge between occipital bone and sphenoid bone seen inside articulated skull

temporal bone (Mandibular Fossa)

oval basin/depression on inferior of bone; located anterior to external acoustic meatus; articulates with mandibular condyle to form TMJ

temporal bone (External Acoustic Meatus)

large hole on lateral side of bone; canal through which sound enters leading to middle ear and eardrum

temporal bone (Internal Acoustic Meatus)

maller hole on medial side of bone; located on petrous portion

temporal bone (Mastoid Foramen)

small hole on superior, posterior part of mastoid process

temporal bone (Stylomastoid Foramen)

hole between styloid process & mastoid processes

temporal bone (Jugular Foramen)

large hole on petrous portion of bone where joins occipital bone; near internal acoustic meatus; passageway for jugular vein; only seen in articulated skull

temporal bone (Carotid Canal)

large, deep opening on inferior side of petrous portion of bone; passes through petrous portion; passageway for carotid artery