COMPANA LE2: Axial Skeletal System

Skeleton

Composed of rigid parts that are attached to muscles

Locomotion

Skeleton is powered by contractions of the muscles

Basic functions of the skeleton

Provision of body shape

Weight support

Facilitation of motility

Protection of soft parts (nerves, major blood vessels, viscera)

Skeleton compoition

Mineralized connective tissue: bone, cartilage, dentin, enamel

Exoskeleton and Endoskeleton

Two kinds of skeleton

Exoskeleton

Within the integument

Endoskeleton

Deep, within the body

Keratinized exoskeleton

From the epidermis

Bony exoskeleton

From the dermis

Bony endoskeleton, cartilaginous exoskeleton, and notochord

Types of endoskeleton

Matrix

Protein fibers and groundsubstance

General connective tissues

Loose and Fibrous

Loose connective tissues

Mesenchyma, adipose, areolar

Fibrous

Dense connective tissue

Special connective tissues

Cartilage, bone, haemopoietic tissue, and blood

Cartilage

Composed of chondroitin sulfate + collagenous or elastic proteins

Cartilage

Hyaline, Elastic, and Fibrous

Hyaline cartilage

Glassy. Persists at the articular ends of long bones, at the tips of ribs, in tracheal rings, and in many parts of the skull. Collagen fibrils = not sufficient in abundance.

Elastic cartilage

Flexible and springy. Internal support for your ear and epiglottis.

Myeloid haemopoietic tissue

Inside cavities

Lymphoid haemopoietic tissue

In spleen, lymph nodes

Bone matrix

collagen fibers + hydroxyapatite crystals + cementing substance

Hydroxyapatite

3Ca3(PO4)2 Ca(OH)2

Water and mucopolysaccharides

Cementing substance of bone matrix

Osteoblasts, osteocytes, osteoclasts

Bone cells

Osteoblasts

Bone forming cells

Osteocytes

Mature bone cells

Osteoclasts

Resorb or break down bown

Calcitonin and parathyroid

Hormones in regulating bone function

Bone cancer

Most painful form of cancer due to pain receptors

Mineralization

general process wherein various inorganic ions are deposited in the organic matrix of tissues to harden them

Calcification

specialized type of mineralization wherein calcium carbonate (invertebrates) or calcium phosphate (vertebrates) is deposited in the organic matrix

Ossification

specialized type of calcification, unique to vertebrates, involving the deposition of hydroxypatite (calcium phosphate) in the organic matrix

Hyaline cartilage

LOCATIONS: Between tips of ribs an bones of sternum; covering bone surfaces at synovial joints; supporting larynch (voice box), trachea, and bronchi; forming part of nasal septum.

Hyaline cartilage

FUNCTIONS: Provides stiff but somewhat flexible support; reduces friction between bone surfaces

Hyaline cartilage

Elastic cartilage

LOCATIONS: Auricle of external ear; epiglottis; auditory tube; cuneiform cartilages of larynx

Elastic cartilage

FUNCTIONS: Provides support, but tolerates distortion without damage and returns to original shape

Elastic cartilage

Fibrous cartilage

LOCATIONS: Pads within knee joint; between pubic bones of pelvis; intervertebral discs

Fibrous cartilage

FUNCTIONS: Resists compression; prevents bone-to-bone contact; limits relative movement

Fibrous cartilage

Cartilage matrix

collagen fibers + sulfated mucopolysaccharide (e.g. chondroitin sulfate)

Chondroblasts and chondrocytes

Cartilage cells

Cartilage

Avascular: diffusion-mediated gas and nutrient exchange

Spongy bone

* also called cancellous or trabecular bone
* have branching structures called trabecular
* contain red bone marrow

Compact bone

* also called cortical bone
* made up of osteons and have occentric layers
* contain yellow bone marrow

Cortical bone

Outer boundary or cortex of a bone

Medullary bone

Lines the core of the bone

Cellular bone

characterized by a matrix that has enclosed osteoblasts or osteocytes

Acellular bone

characterized by a relatively featureless matrix that lacks these bone-forming cells.

Vascular bones

Contains blood vessels

Avascular bones

Does no contain blood vessels

Non-lamellar bone

* fibrolamellar bone; woven bone
* Characterized by the disorderly, irregular arrangement of collagen within the matrix
* Typical of fast-growing bone

Lamellar bone

* mature bone
* characterized by the orderly, regular arrangement of collagenous fibers within the matrix, usually accompanied by the regular orientation of bone cells
* Typical of slow-growing bone

Cellular bone

Acellular bone

Vascular bone

Avascular bone

Non-lamellar bone

Lamellar bone

Endochondral bone

* process of bone development from hyaline cartilage
* forms most of skeleton

Diaphysis

Region of bone; Middle shaft

Epiphysis

Region of bone; Both ends

Metaphysis or epiphyseal plate

Region of bone; region between two ends

Spikelike trabeculae

transitional composites of new bone and resorbing calcified cartilage

Trabeculae

Bone spicules

Dermal bones

* form directly through ossification of mesenchyme


* lies within the dermis of the skin
* ex: skull, pectoral girdle, and integument

Sesamoid bone

* form within tendons


* derived from connective tissues
* ex: patella of the knee and the pisiform bone of the wrist

Perichondral and periosteal bone

* formed from the deep cell layer of the fibrous connective tissue covering cartilage (perochondrium) or bone (peristoneum)


* develops early and retains the ability to form bone directly in adult

Surface bone formation

Appositional growth

Compact bone

* lamellar, with concentrically arranged, mineralized bundles of collagen around a central canal
* Osteon (haversian system): unit of compact bones
* superficailly lined with periosteum

Spongy bone

* characterized by trabecular organization


* trabecula: assemblage of beams, bars, and rods with cavities in between
* trabecular cavities: lined with endosteum and contain marrow

Dentine

* odontoblasts not trapped within lacunae during osteogenesis
* with dentinal tubules resulting from protoplasmic processes left in canaliculi

Enamel

* cells: Ameioblasts
* superficially located


* more superficially than dentine

Acellular bone (aspidin)

* osteoblasts retreat and do not leave processes or canaliculi behind
* modern bony fishes scales


* cementum of vertebrate touch

Joint (Arthrosis)

junction between two bones or cartilages

Diarthrosis

freely movable in at least one plane

Amphiarthrosis

Limited movement

Synarthrosis

Sutured, immovable

Symphysis

Midline joint, very limited movement

Diarthrosis

defined by a synovial (or joint) capsule whose walls consist of dense fibrous connective tissue lined by a synovial membrane, which secretes a lubricating synovial fluid into the confined space; the ends of contacting bones are capped with articular cartilage.

Synarthrosis

lack synovial structures (capsule, membrane, fluid) and, in this, are structurally distinguished from diarthroses.

Synostosis

Bone connection; represents the fusion of formerly separate bones, the firm union is regarded as ankylosed.

Synchodrosis

Cartilage; formed at the midline, are termed symphyses

Syndesmosis

* fibrous connective tissue
* sutures

Membrane bone

* Bone deposited directly within a membranous blastema without having been preceded by a cartilaginous model
* May be compact or spongy, and lamellar or non-lamellar.
* Lacks haversian canal
* E.g. Periosteal bone

Replacement bone

* Deposited where hyaline cartilage already exists
* Undergoes degenerative changes and disappears
* Eroded and replaced by compact bone, spongy bone, or a marrow cavity, depending on its location

Skeletal remodeling

Regional components of the skeleton

Heterotropic bones

develop by endochonral or intramembranous ossification in areas subject to continual stress in amniotes.