4 Types of Bone Cells

1. Osteoprogenitor Cells

- found within the endosteum membrane

- can differentiate into Osteoblasts

2.Osteoblasts

-use mineral salts and calcium to produce new bone

-can differentiate into Osteocytes

3.Osteocytes

-mature bone cells that maintain bone

4. Osteoclasts

-thought to develop from leukocytes

-functions in breaking down or resorption of bone

-releases calcium

          “Too many Osteoclasts can cause the release of too much

            calcium resulting in Osteoporosis.”

                                   differentiate into                        differentiate into

Osteoprogenitor Cells    =     Osteoblasts     =      Osteocytes

                                               (produce new bone)     (maintain bone)

                         differentiate into

Leukocytes     =     Osteoclasts           

                                 (break down bone)

.

The Epiphyseal Plate

The Epiphyseal Plate

A cartilaginous “growth” plate located between the ends of bones

(the epiphysis and the metaphysis) which allows for lengthwise bone growth

4 Zones of the Epiphyseal Plate

1. Zone of Resting Cartilage

-toward Diaphysis

               -small, scattered chrondrocytes that anchor or glue the epiphyseal plate

                to the epiphysis

2. Zone of Proliferating Cartilage

               -dividing chrondrocytes, scattered and stacked

3. Zone of Hydrotrophic (growing) Cartilage

               -chrondrocytes growing

               -stacked in columns for lengthwise growing

4. Zone of Calcified Cartilage (adjacent to Diaphysis)

            -mineral salts deposited in cartilage matrix which changes it to bone

There are 2 Different ways that bone forms:

1. Intamembranous Ossification

-future bone begins as a fibrous connective tissue membrane and  changes into a bone.  Example:  Skull

2. Endochondral Ossification

               -future bone begins as a hyline cartilage model

               - the most common way bones are formed

               -Example: Epiphyseal Plate

Bones

Bones -- Terminology
Canaliculi		The canaliculi connect all bone cells to the nutrient supply, keeping them well-supplied in spite of their hard matrix material
Cartilage		Tough connective tissue covering the ends of the bone. The cartilage reduces friction and acts as a shock absorber.
Haversian canals		central canals carrying the blood vessels and nerves. The Haversian canals run lengthwise through the bone
Haversian system		each complex of a Haversian canal and it's matrix rings
Lacunae		tiny cavities arranged in concentric circles, called lamellae
Lamellae		circles of lacunae and Osteocytes about the central Haversian canal
Ligament		Fibrous tissue that connects bones or cartilage to strengthen and support joints.
Ossification		the gradual conversion of cartilage or other tissue into bone
Osteoblasts		build bone and secrete matrix, located on the surface
Osteoclasts		break down bone and secrete alkaline phosphates, located on the surface of the bone
Osteocytes		the mature bone cells, found in tiny cavities within the matrix called lacunae
Osteocytes		mature bone cells found in the lacunae
Compact bone		Compact bone is dense and hard, especially the outer layer of the bone.
Spongy bone		Made up of a lattice work of bone, the spaces are filled with red marrow which produces blood cells.
cuboidal		box shaped
Flat bones		Plate like and highly PROTECTIVE e.g. bones of the skull protect the brain.
Irregular bones		e.g. vertebrae (spine)
Long bones		Slightly curved for STRENGTH with long narrow shafts with knobbly ends (especially found in arms and legs e.g. femur).
Short bones		Tend to be spongy e.g. wrists, fingers, toes and ankles.
Parts of Bones
diaphysis	The shaft of a long bone.
Epiphysis	The knob like end of the bone, often contains red marrow (blood cells).
epiphyseal plate	growth plate - cartilaginous area where a majority of bone growth occurs - Metaphysis
Metaphysis	Region where the diaphysis joins the epiphysis, important in bone growth - epiphyseal plate
medullary cavity	Marrow cavity inside the bone. Contains yellow marrow (fat cells).
periosteum	The dense fibrous membrane covering the surface of bones except at the joints and serving as an attachment for muscles and tendons
Articular cartilage	cartilage that lines the joints
hyaline	cartilage that forms most of the fetal skeleton and is found in the trachea, larynx, and joint surfaces of the adult.

BONE FORMATION

A.   Bone formation is termed osteogenesis or ossification.

Two types of ossification:

1.     Intramembranous ossification is the formation of bone directly from or within fibrous connective tissue membranes.

2.     Endochondrial ossification is the formation of bone from hyaline cartilage models.

B.    Intramembranous ossification forms the flat bones of the skull and the mandible

A typical long bone consists of numerous parts.

1.     The diaphysis is the shaft of the long bone.

2.     The epiphyses are the ends of the bone

3.     The metaphyses are the areas between the epiphysis and diaphysis and include the epiphyseal plate in growing bones.

4.     Hyaline cartilage (articular cartilage) at the ends of the bones reduces friction and absorbs shock at freely moveable joints.

5.     The periosteum is a connective tissue covering of the surface of the bone which contains osteogenic cells, protects bone, assists in fracture repair, helps nourish bone tissue, and serves as an attachment point for ligaments and tendons.

6.     The space within the diaphysis is the marrow cavity.

7.     The endosteum is the lining of the medullary cavity.

Compact Bone

a.     Compact bone is arranged in units called osteons or Haversian systems

b.     Osteons contain blood vessels, lymphatic vessels, nerves, and osteocytes along with the calcified matrix.

c.     Osteons are aligned in the same direction along lines of stress. These lines can change as the stresses on the bone changes.

Spongy Bone

a.     Spongy bone does not contain osteons.

b.      It consists of trabeculae. (a lattice work of bone containing red marrow in certain regions)

c.     It forms most of the structure of short, flat, and irregular bones, and the epiphyses of long bones.



Human A&P  Chapter 5 

     The 4 Major Tissue Types         010910wedhap     11:25

    I. Epithelial      II. Connective      III. Muscle      IV. Nervous

I.     Epithelial Tissue                                                                                             11:55

A word that describes a common  function for all epithelial tissue is Covering.                                                                                                                                                                    

 1.Simple Squamous Epithelium                            12:28

The name breaks down like this:

·       Simple Single Cell Layer associated with areas where

 diffusion is occurring; diffusion can occur across the surface very easily.

·       Squamous – Refers to the shape of the tissue cell which is   Flattened and Polyhedral (multi-sided or diamond like.)

·       Epithelium – means “covering”

Simple Squamous Epithelium tissue lines the

(Lumen- or hole through each blood vessel through which

 blood flows)

·       Simple Squamous Epithelium tissue provides a smooth

or slick surface, or covering, which produces less drag on

 blood flow.)

In this area we refer to this same tissue as “endothelium.”

And the same tissue in the heart is called “endocardium.”

There are 5 different kinds of blood vessels and

 all have this tissue as an innermost lining.

The smallest of the blood vessels are the Capillaries which

 are involved in the exchange of nutrients, wastes and gases

 in the tissues of the blood.

 They are composed wholly of Simple Squamous Epithelium

cells that loop around and form a tube. 

 Capillaries are very tiny blood vessels. They diffuse nutrients,

 gases and waste -right across their surface.

·       Simple Squamous Epithelium also form the air sacs

 in the lungs which are referred to as Alveoli.

 Alveoli - diffuse oxygen into the blood - out of the air that we breathe-

 and carbon dioxide out of the blood -and into the air that we exhale.

·        Alveoli (plural) have a little tube connected to them

called the bronchial.

·       Alveola (singular) thin hollow ball ( air sac in the lungs)

·        made up of thin flat cells, resembling the plates on a

soccer ball.

2. Stratified Squamous Epithelium                        19:00

·       Stratified means “Multiple layers”  (thick)

Associated with areas where friction wears away cells at the surface

 and you need to replace them from beneath.

·       Forms epidermis (the outermost layer of skin)

As Stratified Squamous Epithelium cells are produced, they are alive,

 down deep and as they push toward the surface, their cytoplasm is

replaced by a tough water-proof agent called keratin/ until finally

at the surface of your body these are dead cells. On the outside these

 dead cells are referred to as Cornified or Horny/. It makes you

 waterproof and tough; it resists physical abrasion, and builds up

as calluses on your hands and feet. It literally maintains a barrier

 to keep bacteria out.

It also lines and maintains a barrier to keep bacteria out of the

mouth, portions of the pharynx (throat), anus, and the vagina.

  (Friction wears away cells at the surface of all these areas.)

3. Stratified Columnar Epithelium                                          22:50

·       Columnar – Refers to Shape

·       Associated with Goblet Cells – which are (mucus secreting)

·       Portions of Pharynx where mucus is needed to lubricate

 for food      swallowing.  Also the Esophagus –needs lubrication-

as does the Anal Canal and the Male Urethra (tube leading

from the urinary bladder to the outside of the body)  Without

 mucus being formed inside the urethra, it would become dry

and adhesions would form where it would grow together.

4. Simple Columnar Epithelium                                                   26:22

·       Simple Single Cell Layer associated with diffusion.          26:30

·       Columnar - as with all column shaped cells are

         associated with mucus production.

·       Line the G.I.  tract between the stomach and anus.

The intestines are specifically designed to absorb nutrients

 – using diffusion.

 5. Simple Cuboidal Epithelium                                                 28:04

·       Simple Single Cell Layer associated with diffusion.

·       Cuboidal meaning “Cubed Shaped”

·       Highly Specialized  -   Kidney and Thyroid Glands

II.  Connective Tissue (C.T.)              090110wedhap         29:43 

A. Loose Connective Tissue

1.    Areolar C.T.

·       Attaches skin to underlying tissue (like muscle) 

       (The epidermis and dermis layers are stuck

       together but attached loosely to the muscle

       underneath to allow for movement of the

       body, but returns to its original position.)

·       Fills spaces between organs

·       Supports blood vessels (loosely holds

         veins in place)

     2. Adipose Tissue “Fat”                                        35:00

·       Energy Storage

         (can be converted to A.T.P.)

·       Padding

·       Insulation

B. Dense Connective Tissue                   35:48

1.    Dense Irregular C.T. (stronger than loose c.t.)

·       Irregular –Refers to the arrangement of the

         fibers. Arranged in all directions- makes

         tissue equally strong in all directions

·       Forms the dermis layer of your skin,

           resists tearing.

2. Dense Regular C.T.                                       37:52

·       Has a parallel arrangement of fibers,

         like the grain of wood which makes it

         super strong but only in one direction.

·       If pulled against the grain it will shred

·       Forms Tendons

·       Forms Ligaments

     3. Elastic C.T.                                                     41:48

·       Forms Walls of Arteries  (like Aorta)

·       Walls of Trachea  (Windpipe)

·       Vocal Cords

    

    

C.           Cartilage            090810wedhap                         11:48           

1.    Hyaline Cartilage  Most abundant Cartilage

                                                  in the body                      

·       Support and Flexibility / Consistency of

         rubber

·       Covers the ends of bones at joints,

         therefore at this area we call it

        “Articular Cartilage”

·       it provides a cushion between bones)

·       Forms the embryonic skeleton

2.    Fibro Cartilage                                                 16:40

·       Like Hyaline but has fibers

         embedded in it

·       Stronger / works like rebar in concrete

·       Forms intervetebral discs

3.    Elastic Cartilage                                              18:48

·       Like Hyaline but has “elastic fibers”

         embedded in it

·       Example: External ear

              Epiglottis (the seal on the Glottis)

D. Bone                                                21:00

Compact  Bone

·       Composed of Haversian Systems

        or (Osteons)

·        Each Haversian System, or Osteon

       consists of mineral salts in concentric

       rings or “Lamellae”

(la mell E’)  pg160/192

Spaces between Lamellae are called Lacunae.--23:58 

  (la Koon-E’ ) This space is filled with Osteocytes

                                                                                           Pg158/195

          

·       Small Canals“Canalicali”

(can uh leak’ uh lee) connect the

Osteocytes to the Haversian Canal

 that contains blood vessels and nerves.

·       Osteocytes are mature living bone cells.  

They have to have a root so that nutrients &

waste can be routed to/away- via the-Haversian

 Canal.

·       Compact Bone is Vascular It contains

 blood vessels and nerves.

    

E. Blood                090810wedhap                                  28:28                   

      Liquid Part                        Solid Part

           Plasma                                   Cells and Cell fragments or

                  The Formed Elements” like:

·       Leukocytes  (White blood cell)

         Fight infection

·       Platelets – Involved in Blood Clotting

·       Erythrocytes –o r(red blood cell)

         Transport Oxygen and Carbon Dioxide

   

III.          Muscle Tissue                                            30:28

There are 3 Types of Muscle Tissue

1.   Skeletal Muscle

- Attached to your skeleton

- Voluntary

- Striated (Light & Dark Bands)

- Parallel fibers – pull in 1 direction 

                                  – exam. Bicep

          Anytime you hear muscle fiber it means “muscle cell.”

     2. Cardiac Muscle                                      32:25

·       Associated with the Heart

·       Involuntary

·       Striated

·        Intercalated Discs

(hold cardiac muscle cells together)

·       branching fibers pulling in multiple

         directions

                           ex: Wicker basket & Chinese finger-cuffs

3. Smooth Muscle                                    34:98

·       Associated with hollow internal

         structure

·       Involuntary

·       Non-Striated

·       Cells are spindle shaped

                                                           

IV. Nervous Tissue                 091010 no recording

        1. Neurons

·       Major cell type “multi-polar neuron”

          –spinal cord

·       Function is Communication

2. Neuroglia

§  Many types

§  Helper cells to the Neurons