Bones and Skeletal System

Bone Tissue:

Bone Cross-Section

Microscopic View of Bone Cross-Section Many people are familiar with a hambone as a cross-section of a typical bone. The center of the bone is filled with marrow, and this is surrounded by the hardened bone tissue itself. If you would examine a bit of this hard bone tissue under a microscope, it would look like the picture to the right. In bone, the extracellular matrix is composed of collagen with Ca₃(PO₄)₂ deposited in it. Note that since vitamin C is needed for collagen synthesis, getting a little extra while a broken bone is healing would probably be a good idea. Bone tissue is composed of repeating, circular units called Haversian systems. Within each Haversian system, there is a central canal where blood vessels and nerves can be found. This is surrounded by concentric layers of the matrix material called lamellae. The darkly-stained spots are spaces called lacunae which contain the osteocytes.

Bones of the Human Skeleton:

Here’s a skeleton
(edited from Corel Presentations 8)

The main bones in the human skeleton include:

cranium

the bones of the skull surrounding the brain, not including the face bones; the bone just above/in front of the ear is the temporal bone

mandible

the jaw bone, so the hinge of the jaw is the temporo-mandibular joint, and problems with malfunctioning of this joint are known as TMJ

vertebrae

bones which make up the spine, which include:

cervical vertebrae

the vertebrae in the neck region

thoracic vertebrae

the vertebrae with ribs attached

lumbar vertebrae

the vertebrae in the lower back

sacrum

five fused vertebrae which are joined to the pelvis

coccyx

four fused vertebrae which comprise the tailbone

ribs

bones protecting the chest cavity (we all have twelve pairs)

sternum

the breastbone

clavicle

the collar bone

scapula

the shoulder blade

humerus

the top of the arm

ulna

the little finger side of the lower arm which also forms the elbow

radius

the thumb side of the lower arm; the Radius Rotates around

carpals

the wrist bones
— Watch out for sound-alike words (Thanks to a very observant student for catching this!): “carpal” refers to a wrist bone, while “carpel” refers to a female flower part.

metacarpals

the palm of the hand

phalanges

the fingers and toes

(os) coxa

Hip Bones (clipart edited from Corel Presentations 8) the hip bones, which include:

ilium

the big bone on top that we think of as the hip bone — Watch out for sound-alike words: “ilium” refers to a hip bone, while “ileum” refers to the last section of the small intestine.

ischium

the bones on which you sit

pubis

the lower front hip bone

ways to tell male pelvis from female:

1. spread of ilium: female more flared and cradle-like with anterior iliac spines farther apart vs. more straight “up-and-down” in male
2. shape of hole in ischium: smaller and triangular in female vs. larger and rounded in male
3. angle across pubic symphysis = pubic arch: less than 90° (acute angle) and more sharply angled in male, greater than 90° (obtuse angle) and more rounded in female
4. inner diameter and distance between ischia larger in female — big enough for head of baby to pass through

femur

the thigh bone

patella

the kneecap

tibia

the thick, inside (big-toe side) shinbone
The root word “tibia” means “flute.” There is a Celtic song “The Two (Twa) Sisters” or “The Wind and the Rain” about a woman who was drowned by a jealous sister. Most versions of this song tell of a minstrel who made her hair and breastbone into a harp which sang of her death. However, I have heard a version (I’m having trouble finding out who recorded it — does anyone out there have any info?) in which, when her bones washed ashore, the man made a flute out of her tibia, which then sang the song of her murder.

fibula

the thin, outer (little-toe side) shinbone

tarsals

the heel bones

metatarsals

the arch of the foot, the sole

phalanges

the fingers and toes