Chapter 7
Bone Function
Support, Protection, and Movement
• Bones give shape to body structures
– Ex. Bone of the skull and face
• Bones provide support and protection
– Ex. Bone of the lower limbs, pelvis, and vertebral
column support the weight of the body
– Ex. Bones of the rib cage and shoulder girdle
protect the heart and lungs
• Bones interact with muscles to make the body
move
Blood Cell Formation
• Hematopoiesis
– Process of blood cell formation
– Begins in the yolk sak (lies outside the embryo)
– Later in development, blood cells are
manufactured in the liver and spleen
– Even later in development, blood cells are formed
in the bone marrow
Blood Cell Formation
• Marrow
– Soft, netlike mass of connective tissue
– Found in:
• the medullary cavity of long bones
• the irregular spaces of spongy bone
• the larger central canals of compact bone
Blood Cell Formation
• Marrow
– 2 types: red marrow and yellow marrow
Blood Cell Formation
• Red marrow
– Functions in the production of red blood cells
(erythrocytes), white blood cells (leukocytes), and
blood platelets
– Has a red color due to the oxygen-carrying pigment
hemoglobin that is found in the red blood cells
– Occupies the cavities of most bones in infants but is
mostly replaced by yellow marrow as individuals
get older
• In adults, red marrow is found primarily in the spongy
bone of the skull, ribs, sternum, clavicles, vertebrae, and
hipbones
Blood Cell Formation
• Yellow marrow
– Stores fat
– Is inactive in blood cell production
– Can change back into red marrow to produce blood
cells if the blood cell supply is deficient
Inorganic Salt Storage
• Inorganic salts account for about 70% (by
weight) of the extracellular matrix of bone
tissue
• Most inorganic salts are small crystals of a
type of calcium phosphate called
hydroxyapatite
– Calcium is required for metabolic processes such
as blood clot formation, nerve impulse
conduction, and muscle cell contraction
Inorganic Salt Storage
• Maintenance of calcium level is controlled
through a negative feedback system:
– When blood is low in calcium, parathryoid
hormone stimulates osteoclasts to break down
bone tissue, releasing calcium from the
extracellular matrix into the blood
– When blood is high in calcium, calcitonin
(another hormone produced by the thyroid)
stimulates osteoblasts to form bone tissue,
storing excess calcium in the extracellular matrix
Inorganic Salt Storage
Inorganic Salt Storage
• Bone tissue also stores smaller amounts of
magnesium, sodium, potassium, and
carbonate ions as well as accumulates
harmful metallic elements such as lead,
radium, and strontium