Anatomy and Physiology

Test 1

Bones (framework), Cartilage (growing/joint), Connective Tissue (ligaments to connect bone)

Primary Components of the Skeletal System

Mobility/movement, support and protection, Hemopoiesis, storage

Skeletal System Functions

Bones form a system of levers that act as attachment sites for skeletal muscles allowing for mobility

Mobility/movement

Bones create a structural framework for the body protecting many delicate tissues

Support and Protection

Formed elements of the blood (RBCs, WBCs and platelet) develop in the red bone marrow of bones

Hemopoeisis

Mineral Storage: 99% of the body’s calcium and phosphate is found in the bones

Lipid Storage: adipose tissue (fat) is stored in yellow bone marrow

Storage

Example of a Long Bone

Femur

Example of a short bone

Tarsal Bone

Example of a Flat bone

Frontal Bone

Example of a Irregular Bone

vertebrae

1/3 Matrix is ___

Organic

2/3 Matrix is ____

Inorganic

Osteoid produced by osteoblasts

Ground substance consisting largely of collagen, proteoglycans and glycoproteins arranged in a uniformed pattern

Gives bone tensile strength by resisting stretching, contributes to bone flexibility

Vitamin C required for collagen formation

Organic

Mineralized crystals (largely hydroxyapatite [Ca10(PO4)6(OH)2]) are deposited around collagen fibers of the osteoid resulting the mineralization/calcification of the bone matrix

Hardened matrix accounts for relative rigidity of bones

Vitamin D necessary for proper calcium absorption

Inorganic

Collagen Fibers and Proteoglycan & Glycoproteins in the Extracellular Bone Matrix are ____

organic

Hydroxyapatite crystals in the Extracellular Bone Matrix are ____

Inorganic

What are the four Bone cells

Osteoprogenitor cells, osteoblasts, osteocytes, and osteoclasts

Derived from mesenchymal stem cells

Differentiate into osteoblasts

Osteoprogenitor cells

Synthesize and secrete osteoid (largely collagen)

Regulate osteoclast differentiation and activity

osteoblasts

Mature cells enveloped by calcified osteoid

Maintains matrix and responds to stress by activating osteoblast and osteoclast activity

Osteocytes

Phagocytic, multinucleated cells that form by the fusion of bone marrow cells

Digests and dissolves bone matrix through resorption

osteoclasts

Located at bone exterior

Appears white, smooth, and solid

Composed of osteons and lamellae

Compact Bone

(Dense or cortical bone)

Located internal to compact bone

Appears porous, with space between bone tissue containing red bone marrow

Composed of trabeculae

Spongy Bone (Cancellous or trabecular bone)

Rings of compact bone that surround the entire outer compact bone surface; found immediately internal to bone periosteum

External Circumferential Lamellae

Compact bone remains of a partially resorbed osteon

found between newer, complete osteons

Interstitial lamellae

The functional unit of compact bone composed of concentric lamellae and a central canal

Lamellae (collagen fibers) are parallel

Each level the Lamellae parallel an opposite way creating a pattern

Inorganic crystals deposited in between the collagen fibers

Osteon

Rings of compact bone that line the inner edge of compact bone tissue; found adjacent to the endosteum

Internal circumferential Lamellae

Double layer bone covering adjacent to compact bone (external circumferential lamellae)

Connected to compact bone by Perforating Fibers

Outer fibrous layer composed of connective tissue

Inner cellular layer (contains osteoprogenitor cells, osteoblasts, and osteoclasts

Periosteum

Incomplete cellular layer that lines the canals and internal circumferential lamellae in compact bone

Contains contains osteoprogenitor cells, osteoblasts, and osteoclasts

Endosteum

Osteoblasts that become surrounded by mineralized bone matrix develop into ____

osteocytes

Osteocytes are located between adjacent concentric ____

Lamellae

The osteocyte cell body is housed in small open spaces called

Lacuna

Cellular processes extend from the osteocyte cell body through thin, small spaces called____ allowing cells to communicate with each other through gap junctions

Canaliculi O

Osteocytes communicate through ___ _____ and send cellular processes to the central blood supply allowing for the exchange of nutrients, wastes, and respiratory gases

Gap junctions

Osteocytes monitor ____ and respond by stimulating ___, initiating bone deposition

stress, osteoblasts

In the spongey bone this forms an open lattice of narrow rods and plates of bones called ___

trabeculae

Spaces between trabeculae are filled with ___ and___

blood vessels, bone marrow

Outer surface of trabeculae covered by an _____

incomplete endosteum

In what type of bone is no medullary cavity present, but bone marrow is found within spongy bone

Flat, irregular, and short bone

Contains medullary cavity

Diaphysis, epiphyses, metaphysis, epiphyseal line, epiphyseal plate

Long bone

Medullary cavity contains two types of highly vascularized bone marrow which are ____ and _____

Red and Yellow

____ is hemopoietic tissue containing highly active stem cells for the formed elements of blood

Red Bone Marrow

_____ is composed largely of adipose (fat) tissue

Can convert back into red if under stress

Yellow Bone Marrow

In a child _____ is present in both the medullary cavity and within the spongy bone of the epiphyses

red bone marrow

In an adults ______ is present in the medullary cavity of long bone and _____ is present within the spongy bone of the epiphyses

Yellow bone marrow, red bone marrow

Enlarged surface ends (“knobs”) composed of a thin outer compact bone layer surrounding inner, bone marrow filled spongy bone

Epiphyses (Proximal & Distal)

Protective hyaline cartilage layer found on some bone ends such as where joints occur

Reduces friction and absorbs shock in moveable joints

Articular Cartilage

Region that widens and transfers the weight between the diaphysis and epiphysis

Contains the cartilage containing epiphyseal plate, or growth plate, responsible for the lengthwise growth in bones

Metaphysis

contains cartilage; growth still occurring

epiphyseal plate

no cartilage present; growth ceased

epiphyseal line

A double layer sheath that covers the outer surface of most bones

Protects bone from surrounding structures, anchors blood vessels and nerves, acts as attachment site for ligaments and tendons

Periosteum

Part of the periosteum: Anchors blood vessels (nutrient foramen) and nerves to bone surface; Attachment site for ligaments and tendons

Outer Fibrous Layer

Part of the periosteum: Contains osteoprogenitor cells, osteoblasts, osteoclasts

Inner Cellular Layer

An incomplete cellular layer containing osteoprogenitor cells, osteoblasts, and osteoclasts

Lines the canals of compact bone, covers spongy bone tissue, and lines the medullary cavity in long bones

Endosteum

Avascular (mature tissue), gel-like protein matrix that includes collagen and aggrecan, a proteoglycan that allows it to absorb water

Unlike bone, there is no calcium present in the extracellular matrix

Extracellular Cartilage Matrix

Dense irregular connective composed mostly of collage fibers that covers cartilage surface and helps maintain its shape

Most of the region contains fibroblasts but the deepest layer contains mesenchymal stem cells

Perichondrium

What are the three cartilage tissue cells

Mesenchymal stem cells, chondrocyte, and chondroblast

Cartilage tissue cell:

Only found only in the deepest layers of the perichondrium

Divides and forms chondroblasts

Mesenchymal stem cell

Cartilage tissue cell:

Maintains the cartilage matrix

Found in individual lacunae

Forms from a chondrobast and may divide and create additional chondroblasts

Chondrocyte

Cartilage tissue cell:

Produces cartilage matrix

Matures into chondrocytes

Found in shared lacunae

Chondroblast

Appositional Growth of Cartilagåe:

Mitotic activity occurs in mesenchymal stem cells within the deepest layers of the perichondrium forming _____. ______ each secrete cartilage matrix causing them to be pushed further and further apart. The chondroblasts mature into _____.

chondroblasts, chondrocytes

Growth occurs at the perichondrium the increases cartilage width

Perichondrium surrounds cartilage in areas such as costal cartilage, between spinal vertebrae and nose; lacking in the articular cartilage of adults

Appositional Growth of Cartilage

Occurs when chondrocytes in the cartilage’s internal region divide

Type of growth that occurs at the epiphyseal plate, allows for an increase in length

Interstitial Growth of Cartilage

Occurs when chondrocytes in the cartilage’s internal region divide

Type of growth that occurs at the epiphyseal plate, allows for an increase in length

Cellular division of chondrocyte produces two new cells (chondroblasts) that occupy a single lacuna

Each cell produces new cartilage matrix and begins to separate from its neighbor

Previously secreted matrix matures, further separating individual cells in their own lacunae

Steps of Interstitial growth

Development of the Skeleton:

tissue is the starting material for the skeletal system structures

Mesenchyme

Development of the Skeleton:

Two ways ossification occurs:

Intramembranous

endochondral

Development of the Skeleton:

mesenchyme directly becomes bone

Intramembranous

Development of the Skeleton:

cartilage forms, then becomes bone

Endchondral

Intramembranous vs. Endochondral Ossification:

Vascularized mesenchymal membrane becomes ossified

Produces flat bones of skull, some of the facial bones, mandible, central part of the clavicle

Intramembranous ossification

Intramembranous vs. Endochondral Ossification:

Hyaline cartilage model becomes ossified

Produces most bones of skeleton including long bones (upper and lower limbs, pelvis, vertebrae, ends of clavicle)

Endochondral ossification

Ossification centers from within thickened regions of mesenchyme

• Mesenchymal cells become osteoprogenitor cells which differentiate into osteoblasts which secrete osteoid

First step to ____

Intramembranous ossification

Osteoid undergoes calcification forming the ossification center

• Calcification of matrix causes osteoblasts to become osteocytes

• Osteoblasts remain at the periphery, continuing to depositing osteoid, allowing for the expansion of the bone deposition

Step 2 of _______

Intramembranous ossification

Woven bone (primary bone) and bone membranes begin to form

• At first, woven bone is formed which is immature and poorly organized (lacking lamellae)

• Mesenchyme tissue condenses and forms the membranes

Step 3 of ______

Intramembranous ossification

Lamellar bone (secondary bone) replaces woven bone

• Lamellar compact and lamellar spongy bone form

• Endosteum and periosteum fully developed

Intramembranous ossification

Fetal hyaline cartilage model develops and perichondrium forms

• Perichondrium develops into periosteum

Step 1 to ______

Endochondral Ossification

Periosteal bone collar forms

• Nutrient foramen starts to develop and interior cartilage breaks down due to mineralization

Step 2 to ______

Endochondral Ossification

Primary ossification center forms

• Periosteal bud blood vessel enters diaphysis

• Cartilage in diaphysis ossifies and bone development extends in both directions toward epiphyses as bone replaces degenerating cartilage

Step 3 to ______

Endochondral ossification

Secondary ossificationcenters form in epiphyses

• Cartilage in epiphyses calcifies, chondrocytes die

• Blood vessels enter carrying osteoprogenitor cells which become osteoblasts active in forming woven bone

• The woven bone in the diaphysis interior is removed by osteoclasts, forming the medullary cavity

• Lengthwise growth occurs at epiphyseal plate until

Step 3 to ______

Endochondral ossification

what are the 5 zones of bone growth

Zone of Resting Cartilage, Zone of Proliferations, Zone of Hypertrophy, Zone of Calcification, Zone of Ossification

Which zone is this:

Mature hyaline cartilage that secures epiphysis to epiphyseal plate

Zone of Resting Cartilage

Which zone is this:

Chondrocytes undergo rapid mitotic division producing longitudinal columns of parallel, flattened lacunae

Zone of proliferation

Which zone is this:

Chondrocytes cease to divide and begin to hypertrophy, walls of lacunae thin

Zone of hypertrophy

Which zone is this:

Minerals deposited between lacunae killing chondrocytes

Zone of Calcification

Which zone is this:

Lacunae walls break down, capillaries and osteoprogenitor cells enter as new bone matrix deposited on the calcified cartilage matrix

Zone of ossification

Multiple _______ may exist in a single bone

____ appear and fuse progressively at set ages

These ages differ among males and females among specific regions with females typically closing at an earlier age

Growth plate fusion on skeletal remains is used to determine age of death in forensics recognizing that the skeleton is sexually dimorphic and variations exist among populations

epiphyseal plates

________ increases bone width

Osteoblasts at periosteum deposit bone matrix in layers parallel to surface

Osteoclasts at endosteum resorb bone matrix along medullary cavity (diaphysis region)

Appositional Growth

Bone Deposition and Resorption:

Adding Bone Tissue

Process of bone matrix being added by osteoblasts

Begins with secretion of osteoid by the osteoblasts, followed by the organized mineralization (calcification) of the matrix

What is this Bone _______

Deposition

Bone Deposition and Resorption:

Removing Bone Tissue

Process of bone matrix being broken down by osteoclasts

Proteolytic enzymes secreted by osteoclasts chemically digest organic matrix components

hydrochloric acid dissolves inorganic matrix producing freed calcium and phosphate ions which enter the blood

What is this bone _____

Resorption

Hormone:

ـــــــــ is necessary for the proper development of growth hormone (GH) which is essential to the formation and maintenance of the skeleton

Thyroid Hormone

Hormone:

_____ released by the pituitary gland stimulates the production of insulin-like growth factor (i.e. IGF) in the liver

_____ IGF enhance mineralization and increases bone density

These hormones have a particularly potent effect on the cartilage within the epiphyseal plate region, stimulating elongation of the long bones

Growth hormone

Hormone:

_____ levels dramatically increase at puberty with both having an especially strong impact at the epiphyseal plate by stimulating both cartilage and bone cells

The growth rate of bone here is greater than that cartilage growth which initiates the closure of the epiphyseal plate, eventually leading to the formation of the epiphyseal line

Postmenopausal women no longer produce significant amounts of estrogen and have an increased risk of osteoporosis

Sex hormone

Steroid hormones released from the adrenal gland that regulate blood glucose levels

High levels cause increased bone loss and impair growth of the epiphyseal plate

______ can be prescribed as anti-inflammatory medications (ex. Asthma treatment) so patients must be monitored since it could potentially have a negative impact on bone growth in children

Glucocorticoids

High levels of serotonin has a negative effect on osteoblast differentiation, may decrease bone density

Serotonin

The ____ hormone and ____ work synergistically to increase blood calcium levels

Parathyroid, Calcitriol

Hormone:

____enhances the production of calcitriol with both hormones working together to increase blood calcium levels

Released in response to decreased blood calcium levels, stimulates bone resorption resulting in an increase in blood calcium levels

Parathyroid

Released by the thyroid in response to high blood calcium levels and in response to exercise; stimulates bone deposition resulting in a decrease in blood calcium levels

Calcitonin

______ states that bone in a healthy person or animal will adapt to the loads under which it is placed

Internal bone architecture adapts as well as external

Mechanical stress occurs in weight-bearing bone due to movement and exercise, required for proper bone remodeling

skeletal contraction and gravitational forces biggest impact

Stress detected by osteocytes which communicates to osteoblasts, triggering an increased synthesis of osteoid that adds to bone strength

Removal of mechanical stress reduces collagen formation and causes demineralization

Immobilization, microgravity environment (space) reduce bone mass

Wolff’s Law

fracture refers to a broken bone that doesn’t penetrate the skin

Simple

fracture occurs when one or more region of a bone pierces the skin

Compound

1.  A hematoma forms from broken blood vessels.

2.  A fibrocartilaginous (soft) callus forms as collagen fibers (from fibroblasts) and dense connective tissue (from chondroblasts) aggregate.

3. A hard (bony) callus forms as adjacentosteoblasts produce bone tissue.

4. The bone is remodeled.

4 steps to bone fracture repair