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Skeletal System Lecture

Class notes for a high school anatomy & Physiology class on the skeletal system

Sarah Norton

on 7 January 2016

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Transcript of Skeletal System Lecture

Skeletal System

Functions of Bones
- Rigid, mineralized structures that make up the skeleton
- fibrous bands that hold bones together into an organized skeleton
- Support
- Protection
- Movement
- Mineral storage
- Hematopoiesis

( Blood cell production in the Marrow)
Types of Bones
Bones are made of 2 types of tissue:
Compact Bone - dense, solid appearance
Cancellous Bone - spongey looking bone matrix
Long Bones
- long cylindrical shape
ex. Femur (thigh bone), Humerous (arm bone)
Short bones
- Cube or box shaped bones
Ex. Carpal (wrist),
Tarsal (ankle)
Flat Bones
- Broad and thin with flattened surface
Ex. Skull, Scapula (shoulder blade), ribs
Irregular Bones
- Often clustered in groups and comes in different sizes and shapes
Ex. vertebrae, facial bones
Sesmoid Bone
- irregularly shaped bones that appear singly rather than in groups
Ex. Patella (kneecap) is the only one
Parts of Long Bone
- Main shaft-like portion
- hollow cylindrical shape
- Both ends of long bones
- Made up of cancellous bone tissue, filled with red marrow
Articular Cartilage
- Thin layer of hyaline cartilage covers the joint surfaces of the epiphyses
- Membrane that covers the bone surface except for the joint surfaces
Medullary Cavity
- Hollow space of the Diaphysis
- filled with yellow marrow
(muscles "pull" on bones)
Parts of Flat Bones
*Fig 7-3*
*Fig 7-4*
- Composed of hard walls of compact bone called the Internal and External Table.
- Thin fibrous membrane that lines the medullary cavity
*Fig 7-5*
Structure of Bone
Compact bone

- Contains many cylinder-shaped units called Osteons
Lamellae - cylinder-shaped layers of calcified matrix (compact, hard)

Lacunae - small spaces between lamellae layers that contain bone cells (osteocytes)

Canaliculi - Tiny canals that radiate in all directions from the lacunae, transport osteocytes.

Central Canal - At the center of each osteon. contains blood vessels and nerves.
Cancellous/Spongy Bone
- Does NOT contain osteons, instead it is made of tiny branches called Trabeculae, which contain osteocytes
ultra-small Canaliculi allows for diffusion of nutrients and waste products
Bone Cells
- Bone forming cells
- In response to stress, hormones, other cell signals
- Bone re-absorbing cells
- Erode bone materials and release into blood stream
- Mature, nondividing osteoblasts
Bone Marrow
- Soft connective tissue called Myeloid tissue

- Infants are born with red marrow, as we age it slowly incorporates more fat, turning into yellow marrow
Red marrow
Yellow marrow
Bone Marrow
- Can be sugically conducted if marrow is diseased or damaged
Regulation of Blood Calcium Levels
High blood calcium levels
decreased osteoclast activity (less breakdown of bone)
Normal blood calcium levels
breakdown of bone (osteoclast activity) increases
Low blood calcium levels
Thyroid increases secretion of calcitonin
Ca++ blood levels decrease
Parathyroid horomone secretion increases
Ca++ blood levels increase
- Bones store 98% of the body's calcium reserves
- During bone formation, osteoblasts remove Ca++ from the blood
- During the breakdown of bone, osteoclasts release Ca++ into the blood
*Fig 7-12*
Development of Bone
Intramembranous Ossification
Endochondral Ossification
- Development of bone from small cartilage model to adult bone
- Bone formation where cartilage develops into
flat bones

stem cells differentiate into osteoblasts

Osteoblasts cluster together in
the center and begin laying
down bone matrix

Matrix calcifies and spreads
- Most bones begin as a cartilage model w/ bones forming from the center (ossification center) outward


- Primary Ossification Center - forms in the center of the diaphysis once blood vessels form and extend to the epyphyses
- Secondary Ossification Centers form at the center of the epiphyses
Frontal bone
Zygomatic bone
Vertebral Column
The lies between the diaphysis and epiphyses.
- During periods of growth, osteoblasts in the epiphyseal plate synthesize bone matrix and calcify, allowing long bones lengthen
Epiphyseal Plate
Epiphyseal PLate
*Fig 7-15*
Epiphyseal Fracture
Seperation of the diaphysis from the epiphysis at the epiphyseal plate
- common in young athletes
Bone Remodeling
(growth in length)
(growth in diameter)
- New bone develops in patterns which are soon replaced by strong, circular layers called lamellae
- Layers form around a central canal containing blood vessels forming Osteons
Bones grow in length and diameter
Strengthening Bone
During physical activity,
muscles pull on bones and stimulate
osteoblasts to lay down more bone matrix
Let's Practice
What are the 3 types of bone cells?
What happens to bone marrow as you age?
Identify the following...
Identify the following types of bones
Name one difference between Intramembranous ossification and endochondral ossification
What is the primary center for bone lengthening in long bones?
Bone Fractures
- a break in the continuity of a bone
- Damages blood vessels that deliver oxygen to osteocytes

- Damage to blood vessels initiates bone repair process

- a Hemotoma, or blood clot, forms
Hematoma is resorbed and replaced by Callus, a special repair tissue that binds the broken ends of the fracture together
some health problems can lengthen fracture healing time such as: osteoporosis,
diabetes, or infections
- Callus tissue begins to turn in to bone
Bone needs to be properly aligned in order to heal correctly
Bone remodeling is complete and fraqcture has healed. (usually occurs within 6 months of injury)
Bone Disorders
- Increased bone porisity and reduced mineral density & mass
- Fracture easily
- Usually associated w/ elderly women but can also occur in men
Rickets and Osteomalacia
(in children)
(in adults)
- Demineralization (loss of minerals) of bone related to vitamin D deficiency

-Rickets involves demineralization in developing bone leading to skeletal defomaties such as "bowing legs"

- Osteomalacia minerals are lost from mature bones.
Eat your Calcium!!
Differences between the male and female skeleton
- bones lighter/thinner
- joint surfaces are small
- wider pelvic cavity (for child birth)
- bones heavier/thicker
- joint surfaces are larger
- very narrow pelvic cavity
Types of Joints
Hinge Joint
ex. elbow and knee
Pivot joint
ex. radius rotating against ulna
Saddle Joint
ex. thumb joint
Ball-and-socket joint
ex. hip and shoulder
Gliding Joint
ex. Wrist, ankle, vertebrae
- Only found in the skull
- Form strong fusions between bones of the skull

Fetal Skull

- Cartilage fills the
space between bones
to allow for rapid
brain growth

Anterior fontanel- large cartilage filled space at where the frontal bone and parietal bones meet (soft spot)
multiaxial movement
uniaxial mobility
slight multi-directionalmovement
biaxial movement
Synovial Joint
- Freely moving joint that joins bones together at the epiphysis via ligament

- Articular cartilage covers the epiphysis at the joint
Uniaxial movement
- Inflammatory joint disease.

- Symptoms: pain, decreased mobility, swelling, and stiffness
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