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Skeletal System

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

Troy Hernandez

on 3 January 2013

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Transcript of Skeletal System

Skeletal System Functions of Bones Bones - Rigid, mineralized structures that make up the skeleton Ligaments - fibrous bands that hold bones together into an organized skeleton - Support
- Protection
- Movement
- Mineral storage
- Hematopoiesis (skull) (calcium/phosphorous) ( Blood cell production in the Marrow) Types of Bones Bones are made up of 2 types of connective tissue:
Compact Bone - dense, solid appearance
Cancellous Bone - open space
with a spongey looking bone
matrix Long Bones - long cylindrical shape ex. Femur (thigh bone), Humerous (arm bone) Short bones - Cube or box shaped bones
- about as wide as they are long 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 Diaphysis - Main shaft-like portion
- hollow cylindrical shape Epiphyses - Both ends of long bones
- Made up of cancellous (spongey) bone tissue, filled with red marrow Articular Cartilage - Thin layer of hyaline cartilage covers the joint surfaces of the epiphyses Periosteum - Dense, fibrous membrane that covers the bone surface except for the joint surfaces Medullary Cavity - Hollow space of the Diaphysis
- filled with yellow marrow Endosteum (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. - The middle is called the Diploe and is made of cancellous bone - Thin fibrous membrane that lines the medullary cavity Bone Tissue - Type of connective tissue also referred to as osseous tissue -The extracellular matrix, or Bone Matrix, is composed of: Inorganic Salts Organic Matrix - Calcified crystals of calcium and phosphate contribute to hardness of bone *Fig 7-5* - Also includes small amount of other minerals like magnesium, sodium, sulfate, and flouride - Composed of bone and connective tissue

- Connective tissue secretes ground substance which is composed of chondroitin sulfate and glucosamine and give bone strength Structure of Bone Compact bone - 80% of total bone mass in the human body
- Contains many cylinder-shaped units called Osteons or haversian systems Osteon Lamellae - cylinder-shaped layers of calcified matrix

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

Canaliculi - Tiny canals that radiate in all directions from the lacunae

Central Canal - At the center of the osteon. contains blood vessels, lymph vessels, and nerves. Cancellous Bone *Fig 7-6* - Does NOT contain osteons, instead it is made of needle like bony branches called Trabeculae, which contain osteocytes ultra-small Canaculi allows for diffusion of nutrients and waste products Bone Cells Osteocyte OsteoBlast Osteoclast - Bone forming cells
- Synthesize bone matrix called osteoid, which mineralize bone tissue - Bone re-absorbing cells
- Giant, multinucleate cells that actively erode bone minerals - Mature, nondividing osteoblasts that have become surrounded by matrix and now lie within a lacuna 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 Infant Child Adult Bone Marrow
Transplant - Can be sugically conducted if marrow is diseased or damaged Regulation of Blood Calcium Levels High blood calcium levels decreased breakdown of bone matrix Normal blood calcium levels breakdown of bone matrix 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 Bone Ca++ Ca++ osteoclast Osteoblast *Fig 7-12* Development of Bone Intramembranous Ossification Endochondral Ossification Osteogenesis - Development of bone from small cartilage model to adult bone - Occurs within connective tissue membranes of flat bones
- Flat bones (i.e. Skull) take shape when stem cells differentiate into osteoblasts

- Osteoblasts cluster together in
ossification center and begin laying
down bone matrix

- Matrix calcifies when Calcium
salts are deposited to form
cancellous bone covered by
compact bone on both sides - 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 Mandible Maxilla Clavicle Scapula Humerus Ribs Sternum Radius Ulna Vertebral Column Sacrum Ilium Femur Tibia Fibula Patella 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 Interstitial
(growth in length) Appositional
(growth in diameter) - New bone develops in chaotic 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 - Osteoclasts enlarge diameter of medullary cavity, while osteoblasts build new bone around the outside Strengthening Bone During physical activity,
muscles pull on bones and stimulate
osteoblasts to lay down more bone matrix Let's Practice What at the 3 types of bone cells? What happens to bone marrow as you age? Identify the following... 1 2 3 4 5 6 Identify the following types of bones 1 2 3 4 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 Osteoporosis - 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 Male Female - 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 Sutures - 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
- Characterized by a synovial cavity
- Articular cartilage covers the epiphysis at the joint Uniaxial movement Arthritis - Inflammatory joint disease
- Synovial membranes
become inflamed and

- Symptoms: pain, decreased mobility, swelling, and stiffness But before we really get started lets have a little fun!! Funny cartoon song time! Clicker question Clicker question 2 Clicker question Human skull has 22 bones, all of which are locked (except for the mandible) along sutures
Cranium – 8 bones
Facial skeleton – 13 bones The Skull Human skull has 22 bones, all of which are locked (except for the mandible) along sutures
Cranium – 8 bones
Facial skeleton – 13 bones The Skull Function:
1. Protect brain
2. provide attachment for muscles
3. house sinuses
Reduce skull’s weight
Increase voice intensity
Lined with mucous membranes, connected to nasal cavity Cranium Frontal bone – forms anterior part of the skull above the eyes
Supraorbital foramen – small opening in the forehead where blood vessels & nerves pass through
Frontal sinus Bones of the Cranium Parietal bone – just behind frontal bone on either side of the skull
Fused at midline to from sagittal suture
Fused with frontal bone to form coronal suture Occipital bone – joins parietal bones at the base of the skull
Fuses with parietal bones along lambdoid suture
Foramen magnum – large opening where spinal cord connects to the brain
Occipital condyles – rounded processes on either side of foramen magnum, join with 1st vertebrae Temporal Bone – on either side of the skull
Joins parietal bone along squamous suture
External auditory meatus – opening to ear
Mastoid process – rounded process, attachment for neck muscles
Styloid process – pointed projection, attachment for tongue muscles
Zygomatic process – projects from temporal bone to form part of cheek Sphenoid bone – wedged between frontal, temporal, and parietal bone
Stella turcica – saddle shaped structure that holds the pituitary gland
Sphenoidal sinus Fig07.10 Fig07.12 Fig07.13 Fig07.12 Fig07.15 Fig07.14 Flexion/Extension
Flexion – bending so angle between the joint decreases
Extension – bending so angle between the joint increases until the normal anatomical position Types of joint movement Hyperextension – excessive extension, bending beyond the normal anatomical position
Dorsiflexion – flexing the foot at the ankle
Plantar flexion – extending the foot at the ankle Abduction/Adduction
Abduction – moving a part away from the midline
Adduction – moving a part toward the midline Eversion/Inversion
Eversion - Turning the foot so the sole is outward
Inversion – turning the foot so the sole is inward Retraction/Protraction
Retraction – moving part backward
Protraction – moving part forward Pronation/Supination
Pronation – turning the hand so the palm is back
Supination – turning the hand so the palm is forward Elevation/Depression
Elevation – raising a part
Depression – lowering a part Joint The union of two or more bones

Classified by the amount of allowable movement.
Immovable (Fibrous)
Slightly movable (Cartilaginous)
Freely movable (Synovial) Bone are separated by a layer of fibrous connective tissue or cartilage
Ex: skull Immovable (Fiberous) joints Slightly Movable (Cartilaginous) Joints Allow limited movement
Bones connected by fibrocartilage or ligaments
Ex: vertebrae
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