THE SKELETAL SYSTEM BONE TISSUE
Bone tissues is continuously growing,
*Bone marrow consist of developing blood
remodelling and repairing it. It contributes to
cells, adipocytes, fibroblast, and macrophage
the homeostasis of the body by providing
within a network of reticular fibers.
support, protection, the production of blood
* It is present in developing bones of the fetus
cells, and the storage of minerals m inerals and
in some adult bones such as the hip bones, ribs,
triglycerides.
breastbones, vertebrae (backbones), skull and the end of the bones of the arm and thigh.
Tissues working together in the bone:
Bone tissue
cartilage tissue
Dense connective tissue
Epithelium
adipose tissue
Nervous tissue
Osteology – Study of bone
Six Main Function of the bone of the Skeletal System: *Bone Tissues Makes up about 18% of the weight of the body 1. Support *The Skeletal serves as the structural framework for the body by supporting soft tissues and providing attachment points to the tendons of most skeletal muscles. 2. Protection *the skeleton protects the most important internal organs from injury. 3. Assistance in movement *Most skeletal muscles attach to the bones; when they contract; they pull on the bones to produce movement. 4. Mineral Homeostasis (Storage and release) *Bone tissues stores several minerals especially calcium and minerals. *Bone tissues stores about 99% of the body's calcium. 5. Bone Cell production *A connective tissue called the bone marrow produces red blood cells and platelets a proce ss called homeostasis
6. Triglyceride Storage
* Yellow bone marrow consist mainly of adipose cells, which stores triglycerides. The stored glyceride is a potential chemical energy reserve * in a newborn, all bone marrow is red and involve in hemopoiesis. * With increasing age, much of the bone marrow changes from red to yellow
Structures of Long bone Diaphysis * Bone shafts or body – the long cylindrical, main portion of the bone.
Epiphyses * Proximal and distal of the bones. Metaphyses * are the region between the diaphysis and the epiphysis * in a growing, each metaphysis met aphysis contains an epiphyseal plate, length at about ages 18-21, the cartilage in the epiphyseal plate is replaced by bone, the resulting bony structure is known as the epiphyseal plate.
Articular cartilage * is a thin layer of hyaline cartilage covering the part of the epiphysis where the bones form an articulation (joint) with another bone. * Articular cartilage reduces friction and absorbs shock at freely movable joints.
Periosteum * Surrounds the external bone surface wherever it is not covered by articular cartilage. * Some of the cells of the t he periosteum enable bone to grow in thickness, but not in length. * The periosteum protects the bones, assists in
THE SKELETAL SYSTEM BONE TISSUE
fracture repair, helps nourish bone tissues,
daily metabolism, such as the exchange of
serves as an attachment point for ligaments and
nutrients and wastes with the blood.
tendons
* Like osteoblast, osteocytes do not undergo
Medullary cavity or marrow cavity
cell division.
* is a hollow cylindrical space within the
cytes – maintain the tissue
diaphysis that contains fatty yellow bone
4. Osteoclast
marrow in adults.
* are huge cell derived from the fusion of as
Endosteum
many as 50 monocytes and are concentrate d in
* A thin membrane that lines the internal bone
the endosteum.
surface facing the medullary cavity. It contains
* On the side of the cell that faces the bone
single layers of cells and a small amount of
surface, the osteoclast plasma membrane is
connective tissue.
deeply folded into a ruffled border
* the cell release powerful lysosomal enzymes FOUR TYPES OF CELLS 1. Osteogenic cells * unspecialized stem cells derived from mesenchyme , the tissue from w hich almost all connective tissues are formed. * They are only bone cells to undergo cell division; the resulting cells are osteoblast. * Osteogenic cells are found along the inner position of the periosteum, in the osteum, and in the canals within bone that contain blood vessels.
2. Osteoblast (Buds or sprouts) * are bone building cells
and acids that digest the protein and the mineral components of the underlying bone matrix. * this breakdown of bone extracellular matrix, termed resorption is part of the normal development, maintenance and repair of the bone. -clast – cells breakdown extracellular matrix. * In response to certain hormones, osteoclast helps regulate blood calcium level. * they are also target cell for drug theraphy used to treat osteoporosis .
* they synthesize and secrete collagen fibers
Depending on the size and distribution of the
and other organic components needed to build
spaces, the region of the bone may be
extracellular matrix of bone tissue, and they
categorized as compact or spongy. overall,
initiate calcification
about 80% of the skeleton is compact bone and
* As osteoblast surround themselves with
20% spongy bone.
extracellular matrix, they become trapped in their secretion and becomes osteocytes.
Compact bone tissue * contains few spaces and is the strongest form of bone tissue
Note: The ending -blast in the name of the
* it is found beneath the periosteum of all the
bone cell or any other connective tissue cell
bones and makes up the bulk of the diaphysis of
means that the cell secretes extracellular
long bones
matrix.
* provides protection and support and resist the stresses produced by weight and
3. Osteocytes * Mature bone cells * The main cells in bone tissue and maintains its
movement.
THE SKELETAL SYSTEM BONE TISSUE
HAVERSIAN SYSTEM
4. The ends of long bones are supplied by
* Lamellae – concentric rings of matrix around
metaphyseal and epiphyseal arteries, which
the haversian canal
arise from arteries that suplly the associate
* Haversian canal – passage for blood vessels
joint.
and nerves * Lacuane – Structures that contain each osteocytes * Canaliculi – Tiny canals protruding from the lacunae connecting access to haversian canal via lamellae, since the haversian canal allows access to blood vessels for nutrient supply
SPONGY BONE * In contrast to compact bone tissue, spongy
bone tissue does not contain osteons. * Spongy bone consist of lamellae arranged in an irregular lattice of thin columns called
trabeculae. * The macroscopic space between the trabeculae help make bones lighter and can sometimes be fluid with red bone marrow, which contains numerous small blood vessels. * Within each trabecular are lacunae that contain osteocytes * Canaliculi radiate outward from the lacunae * Osteocytes receives nourishment from the blood circulating through the blood vessels in the spaces between trabeculae.
BLOOD AND NERVE SUPPLY OF BONE. 1. Periosteal arteries by nerves * enter the diaphysis through many perforating canals and supply the periosteum and outer part of the compact bone. 2. near the center of the diaphysis, a large nutrient artery passes through a hole in compact bone called nutrient foramen. 3. on entering the medullary cavity, the nutrients arteries divides into proximal and distal branches that supplies both the inner part of compact bone tissue and red marrow as far as the epiphyseal plates.
