Download Chapter 7 Bones Summary

SUBJECT: ANATOMY & PHYSIOLOGY
BIOL 2401
Chapter 7 - Bone Tissue
Bones
1.
Overview of long bones
A. Bones support and protect body organs; serve as levers for the muscles to pull
on to cause movement at joints; store calcium, fats, phosphate, and other
substances for the body; and contain red marrow, the sight of blood cell
production (hematopoesis).
B. Bones are classified into four groups – long, short, flat, and a regular – on the
basis of their shape and the amount of compact or spongy bone they contain.
Bone markings are important anatomical landmarks that reveal were muscles
attach and where blood vessels and nerves pass.
C. Two types of bone tissue: compact or dense bone and spongy or cancellous
bone. The compact bone is made of osteons (bone units) and the spongy bone
trabeculae.
D. Cartilage is also present in bone tissue. Condroblasts make cartilage with is
high in protein and water content. These mature to become chondrocytes in
spaces in cartilage called lacunae (same name as in bones). Cartilage has no
nerves, and little blood supply (avascular), contrary to bone which has a lot.
E. A long bone is composed of the shaft (diaphysis) with two ends (epiphysis).
The shaft is composed of compact bone; its cavity contains yellow marrow (fat)
or red marrow. The epiphysis are covered with hyaline cartilage; they contain
spongy bone (where red marrow is found). Hematopoesis occurs here. Review
Figure 7.3.
F. Review the structure of osteons: concentric rings (lamellae) of osteoid around a
central canal that contains blood vessels and nerves. In the rings are spaces
(lacunae) that contain osteocytes. Fine microscopic channels (canaliculi)
radiate from a lacunae and serve as portals for nutrient distribution from the
blood supply.
G. Osteoid: The organic parts (mostly collagen) of the matrix make bone flexible;
calcium PO4 salts (hydroxyapatite) deposited in the matrix make bone hard and
give strength.
H. Bones form on hyaline cartilage models, or fibrous membranes. Eventually these
initial supporting structures are replaced by bone tissue. Epiphyseal plates
persist to provide for longitudinal growth of long bones (interstitial growth)
during childhood and become inactive when adolescence ends (epiphyseal
lines). Bone growth and diameter is appositional growth and occurs at the
periosteum. The inner layer of connective tissue is called the endosteum and
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DR. DAVID L. COX
SUBJECT: ANATOMY & PHYSIOLOGY
BIOL 2401
lines the medullary cavity. Bone stem cells (osteoprogenitor cells), osteoblasts,
osteoclasts can be found next to both membranes. Review Table 7.1.
I.
Many hormones stimulate bone growth- thyroid hormone (TH), human growth
hormone (hGH), Vitamin D, Vitamin C, estrogen & testosterone, and calcitonin.
Vitamin D is important for Ca absorption from the digestive tract and vitamin C
is necessary for collagen production. TH and calcitonin inhibit osteoclast activity
and stimulate kidneys to release more Ca into urine secretion, and thus this
results in less Ca present in the blood. Two hormones parathyroid (PTH) and
calcitriol decrease bone growth. They stimulate osteoclast activity to put Ca into
the blood stream and inhibit the kidneys excreting Ca into urine.
J. During fetal development most bones of the skeleton form from ossification of
hyaline cartilage (endochondral ossification) as that tissue is permeated with
blood vessels. The bones of the skull and mandible from on membranes
(membranous ossification).
K. Bones changes shape throughout life. This remodeling occurs in response to
hormones (for example PTH, which regulates blood calcium levels) and
mechanical stresses acting upon the skeleton.
L.
Review Figure 7.7 for the anatomy of compact bone (the osteon).
M. Skip zones of bone growth in the epiphyseal plate and the section on fractures.
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DR. DAVID L. COX
SUBJECT: ANATOMY & PHYSIOLOGY
BIOL 2401
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DR. DAVID L. COX