The skeletal system

bone replacement

ongoing replacement of old bone tissue by new bone tissue

gelatinous marrow

yellow marrow replaced with reddish jelly

how many pairs of ribs do we have?

• Both males and females 12 pairs

Does ossification continue in adults?

Yes

Bone classification by shape

long, short, flat, irregular

1. zone of resting cartilage

- Layer closest to end of epiphysis - Resting cells; anchor epiphyseal plate to epiphysis - small chondrocytes in cartilage matrix -looks like healthy cartilage

Functions of bones

- support - protection -movement -hematopoiesis - storage of minerals -energy reserves (marrow)

Ribs 1-7 are called

-true ribs. -At the anterior body wall, the true ribs connect individually to the sternum by separate cartilaginous extensions called costal cartilages.

importance of calcium in diet

-Hormonal controls act to maintain blood calcium homeostasis; not the skeleton's strength or well-being. -If blood calcium levels are too low for an extended period of time, the bones will become weak and contain large holes due to demineralization.

Osteoporosis facts

-affects elderly, especially women -bone resorption proceeds faster than deposition -low estrogen implicated but estrogen replacement now considered risky -leads to fractures

phosphate in bones is needed for

-atp utilization -structure of nucleic acids (dna,rna)

Hematopoiesis

-blood cell production in red bone marrow(located in some spongy bone) -red bone marrow contains stem cells( form all of the blood cell types)

bone

-bones are organs -composed of all tissue types - their primary component is osseous connective tissue -the matrix is sturdy and rigid due to calcification (mineralization)

2. zone of proliferating cartilage

-chondrocytes are undergoing rapid mitosis - stack up in columns

3. zone of hypertrophic cartilage

-chondrocytes stop dividing - start hypertrophy -absorb matrix

Ribs 8-12 are called

-false ribs -because their costal cartilages do not attach directly to the sternum. The costal cartilages of ribs 8-10 fuse to the costal cartilage of rib 7 and thus indirectly articulate with the sternum.

4. zone of calcified cartilage

-few cells thick -calcification of matrix -kills the chondrocytes

The last two pairs of false ribs (ribs 11 and 12) are called

-floating ribs because they have no connection with the sternum.

irregular bones

-irregular shape -do not fit into other bone clasification categories ex) vertebrae and hip

red bone marrow

-looks like thick blood -mesh of reticular fibers and immature cells -hemopoietic means produce blood cells -in adults found in axial skeleton and girdles

bones support and protect:

-provides structural support and serve as a framework for the entire body - bones protect many delicate tissues and organs from injury and trauma

functions of cartilage

-support soft tissues -articular surfaces for joints -provide a model for endochondral bone formation

bone remodeling

-the continual deposition of new bone tissue and the removal (resorption) of old bone tissue -relative rates differ with age

endochondral ossification steps

1. Cartilage model develops: - chondroblasts become chondrocytes -perichondrium develops 2. Cartilage calcification, bone collar develops in shaft -chondrocytes hypertrophy,then die -blood vessels grow toward cartilage -osteoblasts under perichondrium form bone 3. Primary ossification center forms: - perisosteal bud: osteoblasts and blood vessels - 12th week:most have formed 4. Secondary ossification centers: -in epiphysis -some form post natally 4. Cartilage replaced by bone -except articular cartilage,epiphyseal plate 5. Epiphyseal plate ossifies: -forms epiphyseal line -between 10 and 25 -last clavicle

Types of bone fractures

1. simple( transverse) 2. spiral 3. comminuted 4.compound (open) 5. impacted 6. growth plate

Calcium regulation feedback loop

1. calcium level rises above a set point 2. thyroid gland releases calcitonin 3. blood calcium level falls and we return to homeostasis 4. if calcium levels falls below a set point 5. parathyroid glands release parathyroid hormones (PTH) 6. blood calcium level rises and we return to homeostasis

bone fracture healing

1. hematoma 2. fibrocartilagenous callus 3. bony callus 4. remodeling by osteoclasts/osteoblasts

zones of epiphyseal plate morphology

1. zone of resting cartilage 2. zone of profilerating cartilage 3.zone of hypertrophic cartilage 4. zone of calcified cartilage 5. zone of ossification

intramembranous ossification steps?

1.ossification centers form thickened mesenchyme -osteoprogenitors develop, become osteoblasts 2. Oseteid (bone matrix calcifies) -trapped osteoblasts become --osteocytes 3. Woven bone (primary bone) forms,periostium forms (from mesenchyme) 4. Lamellae bone (secondary bone) replaces woven bone, compact and spongy bone form

What is the composition of bone matrix?

1/3 organic, 2/3 inorganic

which percent of the body's reserve of the minerals calcium and phosphate are stored and released by bone

90%

Vitamin A

: activates osteoblasts

the thoracic acts as a protective cage around?

Acts as a protective cage around vital organs, such as the heart, lungs, trachea, and esophagus.

When does intramembranous ossification begin?

Begins when mesenchyme becomes thickened and condensed with a dense supply of blood capillaries and continues with four steps

Endochondral ossification begins

Begins with the hyaline cartilage model

The appendicular skeleton

Bones of the limbs and limb girdles that are attached to the axial skeleton

What makes up the inorganic components of bone matrix?

Calcium phosphate Hydroxyapatite crystals: calcium phosphate and calcium hydroxide

Spongy bone is?

Cancellous,trabecular

What makes up the organic components of the bone matrix?

Cells Collagen fibers Ground substance

Curves of the spinal column

Cervical curvature (concave) Thoracic curvature (convex) Lumbar curvature (concave) Sacral curvature (convex)

articular cartilage of long bone

Covers the external surface of the epiphyses Made of hyaline cartilage Decreases friction at joint surfaces

When does ossification begin?

In the embryo by the 8th-12th weeks

Osteoclasts

Located in howships lacuna Ruffled edge contacts bone Secrete hydrochloric acid -dissolves mineral -osteolysis Has lysomes which secrete enzymes that dissolve matrix

hyaline cartilage

Most common type of cartilage; it is found on the ends of long bones, ribs, and nose, has perichondrium,associated with synovial joints, most bones first modeled in hyaline cartilage.

endochondral ossification produces

Most of the other bones of the skeleton

What is the microanatomy of spongy bone?

No osteons In trabecullae --parallel lamellae --osteocytes in lacunae --canaluculi

The axial skeleton

Portion of the skeletal system that consists of the skull, the thoracic cage, and vertebral column

the thoracic cage provides attachment points for?

Provides attachment points for many muscles supporting the pectoral girdles, the chest, the neck, the shoulders, the back, and the muscles involved in respiration.

How does ossification work?

Skeleton begins forming from mesenchyme Or from cartilage model of bone The models are replaced by hard bone

intramembranous ossification produces?

The flat bones of the skull(cranial vault) Some facial bones(automatic bone,maxilla,the mandible The central part of the clavicle

hematoma formation

Torn blood vessels hemorrhage, forming mass of clotted blood called a hematoma Site is swollen, painful, and inflamed

Vitamin D

absorption and transport of calcium and phosphate

Growth hormone (Pituitary gland)

affects bone growth by stimulating the formation of another hormone, somatomedin which is produced by the liver.

bone formation is complete at which age?

age 2

the subdivisions of the skeletal system

axial and appendicular

the skeletal system includes:

bones of the skeleton, cartilage, ligaments, other connective tissues that stabilize or connect bones

bone remodeling helps maintain____?

calcium and phosphate levels in body fluids , and can be stimulated by stress on a bone

estrogen receptors on osseous tissue affect__________

calcium deposition

Fibrocartilage

cartilage that contains fibrous bundles of collagen, such as that of the intervertebral disks in the spinal cord and the pubic symphis

elastic cartilage

cartilage with abundant elastic fibers; more flexible than hyaline cartilage, ear and respiratory tubing

cartilage cell types

chondroblasts and chondrocytes in lacunae

types of bone fracture treatment

closed- set in place by physical manipulation from outside the body open- surgical placement of pins or screws

The types of osseous tissue

compact bone and spongy bone

appendicular skeleton includes

consists of the bones of the appendages • upper and lower limbs • the bones that hold the limbs to the trunk of the body.

periostium

covers bone everywhere but articular surfaces -two layers -fibrous layer- outermost dense irregular ct --site of tendon attachment -innermost layer: next to compact bone --osteoblasts present in young bone -anchored to bone by perforating fibers(collagen)

Compact bone is?

dense outer layer of bone

metaphyseal blood vessels

diaphyseal face of epiphyseal plate

Somatomedin

directly stimulates growth of cartilage in the epiphyseal plate

epiphysis of long bone

ends of the bone, composed mostly of spongy bone

Kyphosis (hunchback)

exaggerated thoracic curvature

yellow bone marrow

fatty marrow of long bones in adults

intervertebral discs

fibrocartilage pads that separate and cushion the vertebrae

fontanelles are

fibrous regions between cranial bones that are typically present early in life, regions of the brain that remain as membranes

intramembranous ossification leads to the formation of

flat bones of skull,zygomatic(cheek bone), maxilla(upper jaw), madible(lower jaw), collar bone(clavicle), and sesamoid bones

facial bones

form the bones of the face. They also • protect the entrances to the digestive and respiratory systems as well as • provide attachment sites for facial muscles

short bones

generally cube-shaped and contain mostly spongy bone ex) carpals, tarsals

interstitial growth

growth from within, chondrocytes in lacunae undergoes mitosis, two chondrocytes in one lacunae, will push apart and form separate lacuna

_______hormone and ______ hormone regulate and maintain normal activity at the epiphyseal plates until puberty.

growth, thyroid

vascularized

have a good blood supply

medullary cavity of long bone

hollow cavity filled with yellow marrow

Types of cartilage

hyaline, elastic, fibrocartilage

membranous bones are ______ at birth

incomplete

appositional growth

increase in bone thickness -undifferentiated cells divide(mitosis) -one daughter cell remains a stem cell, one differentiates into a committed cell. -committed cell further differentiates into chondroblast -located at edge of cartilage

Parathyroid Hormone (Parathyroid gland):

increases blood calcium levels, stimulates osteoclast activity

Calcitonin (Thyroid gland)

inhibits osteoclast activity

endoskeleton

internal skeleton or supporting framework in an animal

growth patterns of cartilage

interstitial growth and appositional growth, both common during growth, later mostly appositional, in adults there usually isnt growth unless for repair

5. zone of ossification

invasion by capillaries and osteoprogenitor

Scoliosis

is an abnormal lateral curvature that sometimes results during development when both the vertebral arch and body fail to form, or form incompletely, on one side of a vertebra.

Lordosis

is an exaggerated lumbar curvature, often called "swayback," that is observed as a protrusion of the abdomen and buttocks.

kyphosis

is an exaggerated thoracic curvature that is directed posteriorly, producing a "hunchback" look.

Three Main Spinal Curvature Deformities

kyphosis, lordosis, scoliosis

curves of vertebral column and arches of the foot are maintained by ________ and ___________

ligaments, tendons

endostium

lines marrow cavity, incomplete - osteoprogenitor cells -osteoblasts -osteoclasts

long bones

longer than they are wide -have a shaft with heads at both ends -contain mostly compact bone ex) femur, humerus

callus formation

mass of tissue that forms at a fracture site and connects the broken ends of the bone

Osteocytes

mature bone cells

calcium in bones is needed for

muscle contraction, blood clotting, nerve impulse transmission

bone movement

muscles attach to the bones of the skelton -contract and pull on bone -functions as a series of levers

Vitamin C:

normal synthesis of collagen

osteoclasts

not derived from osteoprogenitors -related to macrophages -formed from multiple cells, are multinucleated - involved in bone resorption

kinds of blood vessels

nutrient artery and nutrient vein , metaphyseal blood vessels , periosteal blood vessels

interstitial growth

occurs in the epiphyseal plate as chondrocytes undergo mitosis -growth in length

appositional growth

occurs within the periosteum -growth in diameter, thickness

the skeletal system is composed of

osseous tissue, cartilage, fibrous Connective tissue, blood, nervous tissue.

_______ lay down new bone in circular concentric lamellae

osteoblasts

_______ line tubes (haversian canals) left by osteclasts

osteoblasts

_______ unique to warm-blooded animals

osteoblasts

________ phagocytize collagen fibers and dead osteocytes

osteoclasts

_________ "dig holes" with hydrochloric acid

osteoclasts

_________ degrades calcium

osteoclasts

What is the micro anatomy of compact bone?

osteon (haversian) sytem: basic unit --central haversian canal --concentric lamellae *contains collagen fibers --osteocytes --lacunae --canaliculi: permits intracellular communication Cylinder that runs with long axis of long bone Perforating canals -- contain blood vessels,nerve --run perpendicular to central canals,connect them Circumferential lamelle --internal to periostium ----external to circumferential lamelle --internal to endosteum ----internal to circumferential lamelle --run the entire circumference Interstitial lamellae --remains of osteons

Four types of bone cells

osteoprogenitor cells, osteoblasts, osteocytes, osteoclasts

Ossification

process of bone formation

Osteoblasts

produce new bone, and once osteoblasts become entrapped in the matrix they produce and secrete, they differentiate into osteocytes

herniated disk

protrusion of a degenerated or fragmented intervertebral disk so that the nucleus pulposus protrudes, causing compression on the nerve root

epiphyseal line of long bone

runs btwn the diaphysis and epiphysis and is the remnant of the epiphyseal plate

the most common spinal curvature deformity is?

scoliosis is the most common spinal curvature deformity.

Diaphysis (long bone)

shaft of a long bone

bone marrow

soft tissue that occupies the medullary cavity of a long bone or the spaces amid the trabeculae of spongy bone

osteprogenitor cells

stem cells derived from mesenchyme which produce other stem cells and osteoblasts

Thyroid hormone (Thyroid gland):

stimulates bone growth.

Arthrology

study of joints

periosteal blood vessels

supply superficial osteons on diaphysis

Nutrient artery and vein

supply the diaphysis of a long bone

skeletal system functions

supports our weight, interacts with muscles to produce movement, protection, blood cell formation (red bone marrow), mineral storage:(calcium and phosphate)

growth plate

the area just below the head of a long bone in which growth in bone length occurs; the epiphyseal plate.

bone remodeling occurs where in the bone?

the periosteal and endosteal surfaces of a bone

Osteology

the study of bones

flat bones

thin, flattened, and usually curved -thin layers of compact bone around a layer of spongy bone ex) skull, ribs, sternum

flat bones of the skull

two layers of compact bone -inner table -outer table region of spongy bone sandwhiched between them -called the diploe both layers of compact bone are covered by periosteum

bone is highly ______, especially in regions containing red bone marrow

vascularized

Cartilage connective tissue characteristics

weaker than bone, more flexible than bone, avascular

Metaphysis (long bone)

where diaphysis and epiphysis meet

thoracic cage consists of

• Consists of the thoracic vertebrae posteriorly, the ribs laterally, and the sternum anteriorly.

Effects of hormones

• Control and regulate growth patterns in bone by altering the rates of both osteoblast and osteoclast activity.

Sex Hormones: gonads

• Increase rate of bone formation • Production associated with puberty

Axial Skelton includes

• the skull • the vertebral column • the thoracic cage