Skeletal System 6 Functions

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Functions 5 & 6

• Site of blood cell production – ____________ bone

marrow produces red blood cells from a process called hemopoiesis.

– _____________ bone marrow stores lipids (fats) for energy

Parts of a Long Bone• _________________________________________:

the shaft or long, main cylindrical portion of the bone

• _________________________________________: the extremities or ends of the bone

• _________________________________________: in mature bone, the region where the diaphysis joins the epiphysis.

• _________________________________________: a thin layer of hyaline cartilage covering the epiphysis where the bone forms an joint with another bone

• ______________________________: A membrane around the surface of the bone not covered by articular cartilage.

• _____________________(marrow cavity): The space within the diaphysis that contains the fatty yellow bone marrow.

• _____________________________: The lining of the medullary cavity that consists of osteoprogenitor cells.

Histology• The skeletal system consists of four types

of connective tissue -

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Osseous (Bone) Tissue

• Contains lots of extracellular matrix surrounding widely separated cells.

• The matrix consists of inorganic components -

• And organic components -

4 Types of Cells in Bone1. _________________________________________:

cells that undergo mitosis to become osteoblasts.

2. _________________________________________: cells that form bone, but do not have the ability to divide by mitosis.

3. _________________________________________: a mature bone cell, and maintain the daily cellular activities of bone tissue.

4. _________________________________________: function in bone reabsorption, which is important in the development, growth, maintenance, and repair of bone.

Unique to Bone

• Unlike other connective tissue the matrix of bone contains an abundance of ______________________________________.

• These salts are deposited by osteoblasts in the internal framework formed by collagen fibers.

• The tissue then hardens through a process called _____________________________.

2 Types of Osseous Tissue

• ________________________________ – Contains very few spaces – Forms the external portion of the bones – Provide protection and support

• ______________________________ – Usually does not contain true osteons

(tree ring structures) – Consists of irregular latticework of thin

plates called _______________________________

– These spaces are filled with red bone marrow

How does bone form?

• When a human fetus is developing it is composed of mainly fibrous connective tissue and hyaline cartilage.

• ____________________________________________ (the process by which bones form) begins typically around the sixth or seventh week of embryonic life and continues throughout adulthood.

Endochondral Ossification• The replacement of

____________________________________________.

• Most bones are formed this way by the process is best observed in long bones.

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7. Growth and Maintenance• Growth occurs when cartilage cells are

_____________________________ on the epiphyseal side of the plate while the cartilage cells on the diaphyseal are being ________________________________ and turned into bone.

• The thickness of the plate will remain relatively constant while the bone of the diaphyseal side of the plate __________________________________________ in length.

• This process is controlled by the __________________________________________________.

• The regulatory signals that send out HGH slow down as we get older.

• This causes the cartilage on the epiphyseal side to the plate to stop dividing and eventually the diaphyseal side catches up.

• When the epiphysis and diaphysis _________________________ together then no more bone growth can occur.

Still Growing?

Remodeling

• Like your skin, bone is constantly being ____________________ throughout your life.

• This process goes from the _______________.

• Osteoclasts are responsible for the ________________________________ of bone tissue.

Minerals and Vitamins

• Sufficient amounts of calcium, phosphorus, and sodium are what make the bone matrix _____________________________________.

• _______________________is required for the absorption of calcium from the digestive tract.

• Vitamin C, A and B12 also play a role in bone growth and remodeling.

Mineral Storage

• Your bones are not the only organs that need calcium and therefore act as a storage site for this mineral.

• Your bones also store ___________________________which are required to produce nucleic acids (DNA and RNA).

Calcitonin (CT) and Parathyroid (PTH)• ___________________________ is a hormone released

from the thyroid gland in response to ____________ levels of calcium in the blood.

• It ____________________ osteoclastic activity and promotes bone growth and calcium storage, which brings the levels in the blood down.

• In response to _____________ levels of calcium in the blood, your parathyroid glands secrete a hormone called ____________________________________.

• This ________________________________ the activity of osteoclasts which will release calcium into the blood.

Exercise and Bone

• The bones in your body will alter their strength in response to mechanical stress.

• Bones become stronger under this stress because they increase the deposition of mineral salts.

• However, if mechanical stress is not applied then reabsorption does not happen and your bones become weaker through a process called ____________________________________.

Demineralization• The main mechanical stress on bones results

from weight bearing exercise, and the force of ___________________________.

• If a person is bedridden or is in a cast the strength of the unstressed bone diminished because the ______________________________ of minerals has stopped.

• This is why when astronauts experience weightlessness they lose bone strength (mass) quickly because there is nothing acting on them.

Aging

2 principal events happen to our bones as we age.

1. A loss of calcium from bones – Starts at age ___________for females and accelerates

quickly around age 40-45 because estrogen levels start to decrease.

– In males loss does not typically begin until age _________ – The loss of calcium from bones causes osteoporosis.

2. A decreased rate in protein formation which results in a decreased ability to produce organic bone matrix. This causes more accumulation of inorganic matrix making the bones __________________________.

Osteoporosis• An age related disordered characterized as a

_________________________________ in bone mass resulting in an increased susceptibility to fractures.

• The sex hormone _________________________ normally promote bone formation by stimulating osteoblasts.

• But as we age (especially females) these estrogen levels decrease and bone formation slows down.

• Women are more susceptible to this disordered because estrogen promotes bone formation without the need for an increased amount of calcium deposition.

Symptoms

• Causes shrinkage of back bone and height loss

• Affects entire skeleton even teeth!

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Other Factors that cause Osteoporosis

1. Body build (shorter people have greater risk because they have less total mass)

2. Weight (since adipose is a good source of estrogen that slows bone loss)

3. Smoking 4. Calcium deficiencies and malabsorption 5. Vitamin D deficiency 6. Exercise 7. Certain drugs (alcohol, diuretics, cortisone,

etc.) 8. Premature menopause

Rickets

• A __________________________deficiency in children in which the body does not absorb calcium and phosphorus.

• This results in the bones in the leg _____________________ because the weight of the upper body is too much for them to support.

Herniated (Slipped) Disc

• A _________________________ (sticking out) of the inner, soft elastic material of an intervertebral disc.

Fractures

• A fracture is

• We will look at 6 different kinds – Partial (incomplete) – Complete – Closed (simple) – Open (compound) – Comminuted (multifragmentary) – Compressed

Partial (Incomplete)

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Complete

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Closed (Simple)

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Open (Compound)-

Comminuted (multifragmentary)

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Compressed

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