The Skeletal System

What is the skeleton?

Humans have an endoskeleton that develops from

mesenchyme cells of the mesoderm.

Composed of

Bones

Cartilage

Ligaments: bone-to-bone

Tendons: muscle to bone

What does the skeleton do?

Functions:

Movement

Protection

Shape

Support

The Human Skeleton

Divided into two main regions

Axial skeleton

Spine, rib cage, skull

Appendicular skeleton

Upper Appendages (extremities)

Arms, hands, wrists

Lower Appendages (extremities)

Legs, feet, hips

The Human Skeleton

Articulations: where two bones meet to make a

joint

Surface features: protrusions and edges on the bone

Sites of tendon and ligament attachment

Projections that help form joints

Depressions and openings allowing blood vessels and

nerve fibers to pass

Sites of muscle and ligament

attachment

- Tuberosity – large rounded projection

Sites of muscle and ligament

attachment

- Crest – narrow prominent ridge

Sites of muscle and ligament

attachment

- Trochanter – large, blunt,

irregularly shaped process

(Only found on the femur)

Tubercle

- Tubercle –

small rounded

projection or

process

Epicondyle

- Epicondyle – raised area above a condyle

Spine

- Spine – sharp, slender, often pointed projection

Process

- Process – any bony prominence

Projections that help

form joints

Head

- Head – bony expansion carried on a narrow neck

Condyle

- Condyle – rounded

articular projection

Ramus

- Ramus – arm like bar of bone

Depressions and

openings allowing blood

vessels and nerve fibers

to pass

Meatus

- Meatus – canal like passage way

Sinus

- Sinus – Cavity within bone filled with air and lined with mucous membrane

Fossa

- Fossa – shallow basin like depression in bone

Fissure

- Fissure – narrow, slit like opening

Foramen

- Foramen – round or oval opening through a bone

Axial Skeleton

Made up of the

Skull

Cranial bones

_______ (skull cap)

Cranial base

Facial Bones

Held together by _____

Vertebral Column

Rib cage

Axial Skeleton: Skull

Skull

Cranial Bones

Calvaria (skull cap)

Cranial base

Facial bones

Held together by sutures

Axial Skeleton: Skull

Cranial Bones: Calvaria (skull cap)

parietal

temporal

occipital

frontal

sphenoid

ethmoid

Coronal suture

squamosal suture

lambdoid suture

Axial Skeleton: Skull

Facial Bones

nasal

lacrimal

zygomatic

maxilla

Axial Skeleton: Skull

Cranial Bones

Frontal: makes up the forehead and eyebrow ridges

Upper part of the orbits (eye sockets)

Thicker area above the orbits is the supra-orbital ridge

Temporal: has a flat portion, along with…

mastoid process: where neck muscles attach

styloid process: attachment for neck & throat muscles

tympanic region: contain the ear bones

zygomatic process (arch): forms the cheek bone and articulates with the mandible

Parietal: helps protect brain

Axial Skeleton: Skull

Frontal

Supra-orbital ridge

orbit

Axial Skeleton: Skull

Temporal

zygotmatic arch Tympanic

region

mastoid process

styloid process

Axial Skeleton: Skull

Cranial Bones

Occipital: posterior base of the cranium

Formed of several bones that fuse and leave an opening called

the foramen magnum

Occipital condyles attach the head to the vertebral column

Axial Skeleton: Skull

Mandible:

alveolus, body, condyle,

and ramus

Tooth Anatomy:

crown: covered by enamel

(made of calcium)

Axial Skeleton

Vertebral Column

Flexible column that

protects the spinal cord

Two major types of bone

True (movable) vertebrae

Cervical vertebrae:

supports the head and

allows it to rotate

Axial Skeleton

Thoracic Vertebrae

Has two articulation

points with the ribs;

allows the ribs to flex for

breathing

Lumbar Vertebrae

Larger and thicker than

other vertebrae

Supports most of body’s

weight

Axial Skeleton

False (fixed) vertebrae

Fused to one another;

don’t move

Sacrum: fuses with pelvis

Coccyx: tailbone; attachment

point for muscles of the

upper leg

Axial Skeleton

Rib Cage (thorax): protective structure that also aids in breathing

Costal cartilage

Ribs

True ribs: attach to sternum

False ribs: floating

Sternum

Manubrium

Gladiolus

Xiphoid process: attachment for stomach muscles

Appendicular Skeleton

Superior extremities (upper appendages)

Shoulder girdle

Clavicle (collarbone): long bone that runs parallel to first rib

Attachment for muscles of the arms, back, chest, and neck

Scapula (shoulder blade): flat bone, parallel to vertebrae

Attachment for muscles that move the shoulders and arms

Appendicular Skeleton

Arm Bones

Humerus: largest bone of

the upper arm

Radius: shorter forearm

bone; located thumb side

Ulna: longer forearm bone

Olecranon process (elbow)

Trochlear notch:

articulates with the

humerus

Appendicular Skeleton

Hand Bones

Carpals: wrist bones

Metacarpals: form the palm

of the hand

Phalanges: finger bones

Appendicular Skeleton

Inferior Extremities (lower appendages)

Pelvic bone: supports body weight

Acetabulum: forms the point of articulation with the femur

Obturator foramen: passage for major blood vessels and nerves

Appendicular Skeleton

Inferior Extremities

Leg bones

Femur: longest and

strongest bone of the

body

Tibia (shin bone)

Fibula: smaller, lateral

bone of the leg

Patella (knee-cap)

Appendicular Skeleton

Inferior Extremities

Foot bones

Tarsals: forms ankle

Metatarsals: arch of the

foot

Phalanges: toes

Bone

Bone tissue is called osseus

Bone types (shape)

a) Long (femur, phalanges)

b) Short (carpals, tarsals)

c) Flat (skull bones)

d) Irregular (vertebrae)

e) Sesamoid (patella)

Bone Structure

Bone Structure

External

Periosteum: connective tissue that surrounds the bone

Important in bone growth, maintenance, and healing

Contains blood vessels and nerves providing the nutrition and

nutrition

Where tendons and ligaments attach

Bone Structure

Diaphysis: shaft

Epiphysis: ends of bone;

contain red marrow

Epiphyseal plate: found

between diaphysis and

epiphysis; long bone growth

Hyaline cartilage: covers the

articular surface of bones

Internal Features

Compact (cortical) bone:

rigid outer shell of the

bone; 20% of structure,

80% of weight

Osteon: structural unit of

compact bone tissue

Haversian canal: internal

structure of osteon; blood

vessels and nerves pass

through here

Internal Features

Osteocytes: cell of bone tissue; secrete bone matrix Bone matrix composed of

collagen fibers and osteocalcin (contain calcium salts)

Lacunae: cavities that store osteocytes

Connect to each other and to blood vessels through canaliculi

Volkmann’s canals: carry blood vessels and nerves of the periosteum to the central Haversian canals

Internal Features

Cancellous

(trabecular/spongy)

bone: forms the ends of

the long bones and the

center of the other

bones; 80% structure;

composed of

honeycomb-like network

bony struts; less dense

and more flexible than

compact

Internal Features

Medullary (marrow) cavity: hollow center of long bones; bordered by spongy bone and lined with a thin layer of connective tissue called endosteum (capable of generating new bone cells); filled with bone marrow

Yellow marrow: consists of fat cells; act as food reserve for bone cells

Red marrow: produces red blood cells

Joints

Joints: some accompanied by a bursa that contains

synovial fluid.

Type of movement depends on

The manner in which the bones fit together

The tightness of fit between the articular surfaces

The tension of the tissues forming the articulation

The position of the ligaments, muscles, and tendons

associated with the joints

Joints

Structural

Cartilaginous: cartilage covers the articulating bone surfaces;

example is the pubic bones

Fibrous: articulated bones are attached by fibrous

connective tissue; example is between the radius and

ulna

Synovial: articulating surfaceis coverd with a fluid-filled,

fibrous, connective-tissue sack called the synovial

capsule; examples are elbows and knees

Joints

Functional

Synarthrosis: permit no movement;

Gomphosis: formed by a conical process; it is held in a socket by a

ligament; teeth

Syndesmosis: formed when two bones are joined by one or more

ligaments; example is the joint that holds together the tibia and

fibula in the ankle region

Synchondrosis (symphysis) joints: two bones join together by a

piece of cartilage

Synostosis (sutures): formed by the fusion of two bones

Amphiarthrosis: slight movement

Joints

Diarthrosis: provide variety of movements; synovial joints

Ball-and-socket: wide array of movements; like the hip and shoulder

Condyloid (ellipsoid): occurs where a ball-like articular surface rests against the curve-shaped end of the another articular surface; examples: knee between radius and carpals

Joints

Gliding: side-to-side

movements; carpals

Hinge: permit angular

motion along one

plane; example: elbow,

knee, ankle joint

Joints

Pivot: allows rotation;

example: invertebral

joints

Saddle: resemble a

saddle in which one

articular surface rocks

back and forth upon

another; joint of thumb

Bone Development and Healing

Bone Growth

Bone-forming cells (osteoblasts and osteoclasts)

move into the cartilage pegs helping to sculpt

growing bones

Osteoblasts build bone tissue

Osteoclasts break down bone and cartilage; carve &

sculpt bone

Process

osteoclasts carve out a cavity in the center of the

cartilage pegs

blood vessels begin to grow into bone entering the

cavity, providing nutrients for bone growth and

maintenance

Process

osteoblasts enter and start secreting the bone

tissue to replace the cartilage

compact bone is deposited first, then converted

into spongy bone as the cavity enlarges

Homeostatic Imbalance

Fracture – a break in the bone

Open fracture – bone penetrates through the skin

Closed fracture – bone does not penetrate skin

Greenstick Fracture

Fissured Fracture

Comminuted Fracture

Transverse Fracture

Oblique Fracture

Spiral Fracture

Depressed Fracture

Compression Fracture

Fracture ID practice

Fracture treatment

Closed reduction – physician pulls on bone to

realign bone ends

Open reduction – physician surgically inserts

pins or wires to realign bones

Open Reduction - Mandible

Skeletal System Diseases How would damage to the components affect function?

Shin Splint

Shin Splint: a painful condition of the anterior

lower leg that develop from overuse of the ankle

joint

NOT the same as

a stress fracture

Bone and Joint Problems

Arthritis: a condition causing swelling and

stiffness in the joints

Osteoarthritis: deterioration of the articular

cartilage covering the ends of bones

Bone and Joint Problems Rheumatoid arthritis: a condition in which the

immune system attacks connective tissues

Bone and Joint Problems Ankylosing spondylitis: arthritis that affects

the spine; causes the fusion of the vertebrae

Bone and Joint Problems

Juvenile arthritis: arthritis that affects children

Organ-System Diseases

Gout: a metabolic disorder that causes oxalic

acid build-up severe inflammation of

connective tissues throughout body

Organ-System Diseases

Systemic Lupus erythematosus: an

autoimmune disease that attacks body’s own

proteins and connective tissues

Organ-System Diseases

Scleroderma: connective tissue disorder that

causes thickening of skin and abnormal growth

of connective tissues; autoimmune disease

Organ-System Diseases

Fibromyalgia: disorder that causes widespread

joint pain; no degeneration of tissues… patients

look normal.

Osteoporosis

Osteoporosis: degenerative bone disorder; can

occur at any age

Causes:

Malnutrition or undernutrition (not enough calcium-

rich foods or vitamin D)

Decreased levels of sex hormones

Smoking

Excessive alcohol consumption

A less severe case is bone density loss.

Tooth Decay Tooth decay: tooth destruction caused by bacteria.

Enzymes created by bacteria remove calcium, and

break down matrix of tooth leading to a cavity

Advanced tooth decay leads to teeth loss and

destruction of underlying jawbone structure

Myeloma

Myeloma: a cancer of red bone marrow;

weakens the immune system

Most common treatment is chemotherapy with

thalidomide

Osteomyelitis

Osteomyelitis: inflammation of the bone caused by

bacterial blood infections

Osteonecrosis Osteonecrosis: a condition caused by osteocyte

death due to the obstruction of blood flowv

Aging of the Skeletal System

The Aging process

Bone is regularly broken down as new bone is

added

Rate of bone production is greater in young

people bones are denser, heavier, and larger

As we grow older, osteoclast activity outpaces

the bone rebuilding activity of the osteoblasts.

Hip Joint Replacement