Gross anatomy of long bone Flashcards
(6 cards)
diaphesis
In a long bone, the diaphysis (di-af’ĭ-sis), or shaft, makes up most of the bone’s length and is composed of compact bone (Figure 5.3). The diaphysis is covered and protected by a fibrous connective tissue membrane, the periosteum (per-e-os′te-um). Hundreds of connective tissue fibers, called perforating fibers, or Sharpey’s fibers, secure the periosteum to the underlying bone.
epiphyses
In adult bones, there is a thin line of bony tissue spanning the epiphysis that looks a bit different from the rest of the bone in that area. This is the epiphyseal line. The epiphyseal line is a remnant of the epiphyseal plate (a flat plate of hyaline cartilage) seen in a young, growing bone. Epiphyseal plates cause the lengthwise growth of a long bone. By the end of puberty, when hormones inhibit long bone growth, epiphyseal plates have been completely replaced by bone, leaving only the epiphyseal lines to mark their previous location.
In adult bones, there is a thin line of bony tissue spanning the epiphysis that looks a bit different from the rest of the bone in that area. This is the epiphyseal line. The epiphyseal line is a remnant of the epiphyseal plate (a flat plate of hyaline cartilage) seen in a young, growing bone. Epiphyseal plates cause the lengthwise growth of a long bone. By the end of puberty, when hormones inhibit long bone growth, epiphyseal plates have been completely replaced by bone, leaving only the epiphyseal lines to mark their previous location.
medullary cavity
The inner bony surface of the shaft is covered by a delicate connective tissue called endosteum. In infants, the cavity of the shaft, called the medullary cavity, is a storage area for red marrow, which produces blood cells. Children’s bones contain red marrow until the age of 6 or 7, when it is gradually replaced by yellow marrow, which stores adipose (fat) tissue. In adult bones, red marrow is confined to cavities in the spongy bone of the axial skeleton, the hip bones, and the epiphyses of long bones such as the humerus and femur.
bone markings
Even when looking casually at bones, you can see that their surfaces are not smooth but scarred with bumps, holes, and ridges. These bone markings (described and illustrated in Table 5.1) reveal where muscles, tendons, and ligaments attach and where blood vessels and nerves pass. There are two categories of bone markings: (a) projections, or processes, which grow out from the bone surface, and (b) depressions, or cavities, which are indentations in the bone. There is a little trick for remembering some of the bone markings listed in the table: All the terms beginning with T are projections, and the terms beginning with F (except facet) are depressions.
spongy bone
The appearance of spongy bone and compact bone to the naked eye only hints at their underlying complexity. Under a microscope, you can see that spongy bone is composed of small needlelike pieces of bone called trabeculae and lots of “open” space filled by marrow, blood vessels and nerves
comapact bone
Think of Compact Bone Like an Apartment Building
Osteocytes = People
The osteocytes are bone cells — like the people living inside the building.
They live in little rooms called lacunae (say it like “la-koo-nee”).
Lacunae = Rooms in a Circle
These rooms are arranged in rings, like an onion or a tree trunk.
Each ring is called a lamella (plural: lamellae).
Central Canal = Elevator Shaft
In the middle of each ring is a central canal (also called a Haversian canal).
This is like the main elevator shaft — it brings blood and nutrients to the building.
Osteon = One Apartment Unit
One osteon is one complete “apartment unit” — a central canal with rings of lacunae and osteocytes around it.
The osteon is the basic building block of compact bone.
Canaliculi = Hallways
Tiny canals called canaliculi (say: “kan-a-lick-yoo-lee”) are like tiny hallways.
They connect all the “rooms” (lacunae) to the central elevator shaft (central canal), so nutrients can reach every cell and waste can leave.
Perforating (Volkmann’s) Canals = Side Doors
These canals run sideways across the building, like emergency exits or side hallways.
They connect the outside of the bone to the central canals, so blood and oxygen can get in from outside.
