Bones
“He guards all his bones; Not one of them is broken.” Psa 34:20
“But when they came to Jesus and saw that He was already dead, they did not break His legs.”
John 19:33
“For these things were done that the Scripture should be fulfilled, 'Not [one] of His bones shall
be broken.'"
John 19:36
organs that constitute part of the endoskeleton of vertebrates;
composed of living tissue

Bones are rigid

At birth, there are over 270 bones in an infant human's body, [1] but many of these fuse
together as the child grows, leaving a total of 206 separate bones in an adult. The largest
bone in the human body is the femur and the smallest bones are auditory ossicles. [2]
Functions
Bones have eleven main functions:
Mechanical
 Protection — bones can serve to protect internal organs, such as the
skull protecting the
brain or the ribs protecting the heart and lungs.
 Structure — bones provide a frame to keep the body supported.
 Movement — bones, skeletal muscles, tendons, ligaments and joints function together
to generate and transfer forces so that individual body parts or the whole body can be
manipulated in three-dimensional space. The interaction between bone and muscle is studied
in biomechanics.
 Sound transduction — bones are important in the mechanical aspect of overshadowed
hearing.
Synthetic
marrow, located within the medullary cavity of long bones and
interstices of cancellous bone, produces blood cells in a process called hematopoiesis.
 Blood production — the
Metabolic
 Mineral storage — bones act as reserves of minerals important for the body, most notably
calcium and phosphorus.

Growth factor storage — mineralized bone matrix stores important growth factors such as
insulin-like growth factors, transforming growth factor, bone morphogenetic proteins
and others.
 Fat storage — the yellow bone marrow acts as a storage reserve of
fatty acids.
Acid-base balance — bone buffers the blood against excessive pH changes by absorbing or
releasing alkaline salts.
 Detoxification — bone tissues can also store heavy metals and other foreign elements,

removing them from the blood and reducing their effects on other tissues. These can later be
gradually released for excretion.[citation needed]

Endocrine organ — bone controls phosphate metabolism by releasing fibroblast growth
factor – 23 (FGF-23), which acts on kidneys to reduce phosphate reabsorption. Bone
osteocalcin, which contributes to the regulation of
blood sugar (glucose) and fat deposition. Osteocalcin increases both the insulin
secretion and sensitivity, in addition to boosting the number of insulin-producing cells
and reducing stores of fat.[3]
cells also release a hormone called
Types
There are five types of bones in the human body: long, short, flat, irregular, and sesamoid.
 Long bones are characterized by a shaft, the diaphysis, that is much longer than it is
compact bone, with lesser amounts of marrow, located
within the medullary cavity, and spongy bone. Most bones of the limbs, including those
of the fingers and toes, are long bones. The exceptions are those of the wrist, ankle
and kneecap.
 Short bones are roughly cube-shaped, and have only a thin layer of compact bone
wide. They are made up mostly of
surrounding a spongy interior. The bones of the wrist and ankle are short bones, as are the
sesamoid bones.
Flat bones are thin and generally curved, with two parallel layers of compact bones
sandwiching a layer of spongy bone. Most of the bones of the skull are flat bones, as is
the sternum.
 Irregular bones do not fit into the above categories. They consist of thin layers of

compact bone surrounding a spongy interior. As implied by the name, their shapes are
irregular and complicated. The bones of the spine and hips are irregular bones.

Sesamoid bones are bones embedded in tendons. Since they act to hold the tendon further
away from the joint, the angle of the tendon is increased and thus the leverage of the
muscle is increased. Examples of sesamoid bones are the patella and the
pisiform.
 Periosteum: sheath of tissue that contains blood vessels that supply nutrients to the
bones; also contains nerves that can send pain signals
 medullary cavity: contains bone marrow and blood vessels; red bone marrow produces blood
cells, yellow bone marrow composed of fats stored by the body
 spongy bone: made of minerals and collagen; open spaces in network of solid bone; hard,
providing support; contains red bone marrow which produces red blood cells
 compact bone: made of minerals and collagen packed tightly forming a hard, tough structure
that can withstand strong shocks
Activity
 build a Qtip skeleton
Homework
1. p.291 – questions 1,2,5,7,8,9,11,12
2. skeleton worksheet