Skeletal system

What are the 5 functions of the skeletal system?

1. support (framework)
2. protection (of internal organs)
3. movement (muscles pull on bone)
4. mineral storage (store, release calcium, phosphate)
5. blood cell formation (red marrow)

What is calcium phosphate for?

Calcium phosphate provides structural strength and resilience to bones and teeth, helping them resist stress and maintain their integrity.

What is collagen for?

Collagen provides strength, elasticity, and flexibility to tissues, allowing for lightness and movement in structures like skin, tendons, and bones.

Locomotion

self-movement, manipulating yourself instead of the environment

what are the components of the skeletal system?

1. Bones
2. Cartilage
3. Joints

4 types of bones

long, short (sesamoid), flat, irregular

Describe characteristics of long bone

length>>width
long diaphysis w/ epiphyses at each end that fit into joints

function of long bone

1.) support weight of body
2.) facilitate movement
3.) absorb stress

characteristics of short bone

cube-shaped

examples of long bone

humerus, phalanges, metacarpals, tibia, radius, ulna, fibula

function of short bone + examples

components of wrists & ankle joints
ex. carpals, tarsals

characteristics of flat bone

Thin, flattened, somewhat curved
- usually laying over another body part ie. ribs over lungs

examples of flat bone

cranial bones in skull, sternum, scapula, ribs

Characteristics of irregular bone

varied and complex shape that does not fit into the typical categories of long, short, or flat bones. These bones are often designed to protect internal organs or support specific body structures

function of irregular bone

varied: support, protection, anchor point for skeletal muscle attachment, joint stability

examples of irregular bone

Vertabrae, coxal bones, pelvic bones, mandible

characteristics of sesamoid bone

A type of short bone that is small, round oval shpaed

Function of sesamoid bone

Reinforce tendons, forms in tendons (not directly connected to other bones) and protect from wear& tear

examples of sesamoid bone

Patella, bones in hand (joint where thumb meets hand), bones in feet (big toe)

Osteocyte

bone cell

Organic composition (living bone components)

osteoblasts, osteoclasts, osteoid
- chondroblasts, fibroblasts

chondroblasts

produce cartilage

Fibroblasts

produce collagen fibers

Inorganic composition (non living)

The inorganic component of bone is made up of mineral salts, primarily calcium and phosphate, which give the bone its hardness and strength.

osteoid

Osteoid is the soft, unmineralized bone tissue made by osteoblasts. It serves as the foundation for mature bone, and once minerals like calcium are added, it hardens into strong bone tissue.

osteogensis imperfecta

brittle bone disease where gene defect in specific type of collagen found in osteoid= strength
resulting in fracture w/ very little force

2 types of bone tissue

compact (cortical) or spongy (trabecullar, cancellous)

what is the biggest difference between spongy bone and compact bone?

The main difference is their organization. Spongy bone has a loose, porous structure with trabeculae (lattice-like bone), making it lightweight and ideal for shock absorption. Compact bone has a dense, tightly organized structure with osteons (Haversian systems), providing strength and support.

characteristics of compact bone

organized, dense, solid, heavy, tough, compact

where is compact bone located?

covers outside of all bones

what is an osteon?

structural unit of compact bone

what are osteons composed of?

lamellae

what is lamella

hallow tube made of osteocytes, arranged concentrically to form an osteon

where is haversion's canal located?

center of each osteon
up & down

what do haversion's canal do?

Haversian canals allow blood vessels and nerve fibers to run through the bone, providing nutrients and signals to the bone tissue.

where are volkmann's canals found?

perpendicular to haversian canals (across)

what does volkmann's canal do?

Volkmann's canals allow blood vessels and nerves to flow to and from the central canals (Haversian canals) within bone, helping with nutrient and waste exchange.

characteristics of spongy bone

Spongy bone contains red marrow and is highly vascularized (rich in blood vessels). It has a porous, lattice-like structure that is less dense than compact bone, allowing it to be lightweight while still providing strength. The arrangement of trabeculae (bone strands) is less organized compared to compact bone, but it helps distribute stress effectively.

purpose of spongy bone structure

The lamellae are arranged in a crisscross pattern to form trabeculae, which align along lines of stress. This structure helps resist mechanical stress by redirecting it toward the compact bone, maximizing strength while minimizing mass.

characteristics of epiphysis in long bone

spongy bone surrounded by compact bone, red marrow produces blood cells, articular cartilage

characteristics of diaphysis

bone shaft, medullary cavity (surrounded by compact bone), yellow marrow (adipose tissue)

what are the 2 membranes?

periosteum and endosteum

where is periosteum located

The periosteum is a dense layer of tissue that covers the outer surface of bones, except at the joints, where articular cartilage is found.

functions of periosteum

serves as an attachment site for ligaments and tendons and is the location of osteoblasts and osteoclasts, which are involved in bone growth and remodeling.

function of endosteum

The endosteum lines internal bone surfaces, including the medullary cavity walls and trabeculae in spongy bone. It is also the location of osteoblasts and osteoclasts, which are involved in bone growth and remodeling.

Epiphyseal plate

allows longitudinal growth (length)

yellow marrow

adipose tissue, in medullary cavity/diaphysis

functions of cartilage tissue

Prevent friction, absorption for shock, builds certain structure in the body

water content in cartilage tissue

Cartilage has a high water content, which gives it flexibility and the ability to absorb shock.

3 types of cartilage

Elastic, hyaline, and fibro-cartilage

Elastic cartilage

most flexible, contains elastin, essential ability of bending and snapping back in place + support
ex. Ear

list them from most flexible to least flexible

Elastic, Hyaline, Fibro

what are the 4 subtypes of hyaline cartilage?

articular, costal, respiratory, nasal

what does articular cartilage do?

1.) covers ends of bones at movable joints to prevent bones from rubbing together, reduce chance of excessive rotational movement
2.) reduce friction

characteristics of hyaline cartilage

connective tissue that is smooth, glassy, resilient, lacks blood vessels

what does costal cartilage do?

connects ribs to sternum

what does respiratory cartilage do?

found in internal structures in respiratory system such as trachea, larynx, bronchi

what does nasal cartilage do?

forms the external nose

characteristics of fibrocartilage

fibrocartilage is made of chondrocytes and thick collagen fibers, making it strong and compressible. It absorbs shock and supports weight in areas like intervertebral discs and the knee.

what does fibrocartilage consist of?

organized rows of chondrocytes w/ collagen fibers

What does the axial skeleton consist of?

skull, ribs, vertebrae column

function of axial skeleton

protect internal organs + stores minerals (calcium) + produces red blood cells + supports

what does the appendicular skeleton consist of?

includes the limbs (arms and legs) and the girdles (shoulder girdle and pelvic girdle) that attach the limbs to the axial skeleton.

function of appendicular

facilitates movement (locomotion)

Osteoarthritis

Osteoarthritis occurs when articular cartilage wears away, causing exposed bone surfaces to rub together. This leads to pain, swelling, and limited joint movement.

Rheumatoid arthritis

Rheumatoid arthritis is an autoimmune disease where the body's immune system mistakenly attacks its own joints and sometimes other organs, causing inflammation, pain, and damage to the affected areas.

Parts of body affected by Rheumatoid arthritis

Wrists, hands, ankles, eye, skin, kidneys, digestive tract

where does Osteoarthritis occur

Hands, knees, hips, spine

Function of axial skeleton

Protection, support (head, ribs, vertebrae)

Function of appendicular skeleton

Limbs facilitate movement

1st step of prenatal ossification

A bone collar forms around the diaphysis (shaft) of the cartilage model, marking the beginning of bone development.

2nd step of endochondrol ossification

Calcification (adding in calcium)
- break down of cartilage, primary ossification center

Step 3 of endochondrol ossification

The periosteal bud (a large blood vessel) delivers nutrients to the cartilage model, allowing for the formation of spongy bone.

Step 4 of Prenatal Ossification

The epiphysis and diaphysis become visible, secondary ossification centers form, the medullary cavity develops, and spongy bone in the diaphysis turns into compact bone.

Process of postnatal interstitial growth in the long bone

Region proximal to epiphysis- mitosis of hyaline cartilage cells
- cartilage calcifies and converts to bone tissue as cells migrate through zone

What are the 3 zones

Proliferation zone, calcification zone, ossification zone

Proliferation zone

Chondrocytes (cartilage cells) divide via osmosis and produce new cartilage

Calcification zone

Older chondrocytes enlarge and signal the surrounding matrix to calcify in the calcification zone. The cartilage matrix hardens, and the chondrocytes die, leaving behind calcified cartilage in the shape of trabeculae.

Ossification zone

Osteoclasts digest calcified cartilage and osteoblasts replace it with actual bone tissue

How does a pregnant woman get enough calcium for her baby if her levels are low?

If a pregnant woman’s calcium levels are low, parathyroid hormone (PTH) will be released to help maintain adequate blood calcium levels. PTH stimulates osteoclast activity, leading to bone resorption (breakdown) to release calcium into the blood. This extra calcium can then be used by both the mother and baby. The mother can also increase her calcium intake through diet and supplements to support her and her baby’s needs.

What happens if you take calcium supplements and drink milk—how will you store the extra calcium?

When you have an excess of calcium from supplements or diet, your thyroid gland releases calcitonin. Calcitonin inhibits osteoclast activity and promotes calcium storage in bones. This process helps store the extra calcium in bones, lowering blood calcium levels to maintain balance and prevent high calcium levels in the blood.