Bones and Skeletal Tissue

20- Line

A line is a narrow ridge of bone; less prominent than a crest.

36- Tubercle

A tubercle is a small rounded projection or process.

8- Diaphysis

A tubular diaphysis, or shaft, is what forms the long axis of the bone. A) The diaphysis elongates and a medullary cavity forms. B) In newborn infants, the medullary cavity of the diaphysis and all areas of spongy bone contain red bone marrow.

12- Epiphysis

The epiphyses (singular: epiphysis) are the bone ends. A) In many cases, the epiphyses are broader than the diaphysis. B) An outer shell of compact bone forms the epiphysis exterior and their interiors contain spongy bone.

26- Osteocytes

The spidery osteocytes are mature bone cells that occupy spaces (lacunae) that conform to their shape. A) Osteocytes monitor and maintain the bone matrix. B) Osteocytes also act as stress or strain "sensors" and respond to mechanical stimuli (bone loading, bone deformation, weightlessness).

35- Trochanter

Trochanter is a very large, blunt, irregularly shaped process. A) The only examples are on the femur.

37- Tuberosity

Tuberosity is a large rounded projection; may be roughened.

38- Yellow marrow

Yellow marrow is the fat-tissue found within bone cavities. A) However, yellow marrow in the medullary cavity can revert to red marrow if a person becomes very anemic and needs more red blood cells. B) In adults, the medullary cavity contains fat (yellow marrow) and is called the yellow marrow cavity.

5- Condyle

Condyle is a rounded articular projection.

6- Crest

Crest is the narrow ridge of bone; usually prominent.

7- Depressed fracture

Depressed fracture is when broken bone portion is pressed inward. A) Typical of skull fracture.

21- Meatus

Meatus is a canal-like passageway.

31- Sinus

Sinus is a cavity within a bone, filled with air and lined with mucous membrane.

32- Spine

Spine is a sharp, slender, often pointed projection.

33- Spiral fracture

Spiral fractures are ragged breaks that occurs when excessive twisting forces are applied to a bone. A) Common sports fracture.

10- Epiphyseal line

The epiphyseal line is a remnant of the epiphyseal plate, a disc of hyaline cartilage that grows during childhood to lengthen the bone.

11- Epiphyseal plate

The epiphyseal plate is a plate of hyaline cartilage at the junction of the diaphysis and epiphysis that provides for length in a long bone. A) As adolescence ends, the chondroblasts of the epiphyseal plates divide less often until they are entirely replaced by bone tissue. B) The epiphyseal plate cartilage abutting the diaphysis organizes into a pattern that allows fast, efficient growth.

19- Impacted fracture

An impacted fracture is one whose ends are driven each other. A) Commonly seen in arm fractures in children. B) Also known as a buckled fracture.

30- Simple/closed fracture

Closed (simple) fracture is a fracture where the bone ends do not penetrate the skin. A) A simple fracture of small or medium-sized bones in young adults heals in six to eight weeks, but it takes much longer for large, weight-bearing bones and for bones of elderly people (because of their poorer circulation). B) Repair in a simple fracture involves four major stages (hematoma formation, fibrocartilaginous callus formation, bony callus formation, and bone remodeling occurrence).

1- Comminuted fracture

Comminuted fractures are bone fractures into three or more pieces. A) Particularly common in the aged, whose bones are more brittle.

2- Compact bone

Compact bone is the dense outer layer of the bone that looks smooth and solid to the naked eye. A) Spongy bone is replaced every three to four years; compact bone, every ten years or so. B) Although compact bone looks solid, a microscope reveals that it is riddled with passageways that serve as conduits for nerves and blood vessels.

3- Compound/open fracture

Compound/open fracture is when the bone ends penetrate the skin.

4- Compression fracture

Compression fractures are when the bone is crushed. A) Common in porous bones (i.e., osteoporotic bones) subjected to extreme trauma, as in a fall.

25- Osteoclasts

Derived from the same hematopoietic stem cells that differentiate into macrophages, osteoclasts are giant multinucleate cells located at sites of bone resorption. A) When actively resorbing (breaking down) bone, the osteoclats rest in a shallow depression called a resorption bay and exhibit a distinctive ruffled border which directly contacts the bone. B) Osteoclasts may also phagocytize the demineralized matrix and dead osteocytes.

9- Epicondyle

Epicondyle is the raised area on or above a condyle.

13- Facet

Facet is a smooth, nearly flat articular surface.

14- Foramen

Foramen is a round or oval opening through a bone.

15- Fossa

Fossa is a shallow, basinlike depression in a bone, often serving as an articular surface.

16- Greenstick fracture

Greenstick fracture is when the bone breaks incompletely, much in the way a green twig breaks. A) Only one side of the shaft breaks; the other side bends. B) Common in children, whose bones have relatively more organic matrix and are more flexible than those of adults.

17- Groove

Groove is a furrow.

18- Head

Head is a bony expansion carried on a narrow neck.

34- Spongy bone

Internal to this is spongy bone (also called trabecular bone), a honeycomb of small needle-like or flat pieces called trabeculae. A) In flat bones, the spongy bone is called the diploë and the whole arrangement resembles a stiffened sandwich. B) Spongy bone is replaced every three to four years; compact bone, every ten years or so.

22- Medullary cavity

Medullary cavity is the central cavity of a long bone. A) In adults, the medullary cavity contains fat (yellow marrow) and is called the yellow marrow cavity. B) In newborn infants, the medullary cavity of the diaphysis and all areas of spongy bone contain red bone marrow.

23- Ossification

Ossification and osteogenesis are synonyms meaning the process of bone formation. A) In embryos, this process leads to the formation of the bony skeleton. B) However, ossification in adults serve mainly for bone remodeling and repair.

24- Osteoblasts

Osteoblasts are bone-forming cells that secrete the bone matrix. A) Like their close relatives, the fibroblasts and chondroblasts, they are actively mitotic. B) The unmineralized bone matrix they secrete includes collagen (90% of bone protein) and calcium-binding proteins that make up the initial unmineralized bone, or osteoid.

27- Process

Process is any bony prominence.

28- Ramus

Ramus is an armlike bar of bone.

29- Red marrow

Red marrow is the blood-forming tissue found within bone cavities. A) The red marrow found in the diploë of flat bones (such as the sternum) and in some irregular bones (such as the hip bone) is much more active in hematopoiesis. B) Hematopoietic tissue, red marrow, is the substance found within the trabecular cavities of spongy bone of long bones and in the diploë of flat bones.