ANAT3001 - Cartilage and Bone & Skeleton

Cartilage

A connective tissue that is more flexible than bone and that protects the ends of bones and keeps them from rubbing together.

Functions oF Cartilage

1. Support and protect soft tissue.

2. Cover ends of bones at joints.

3. Provide a model for bone formation.

Characteristics of Cartilage

Perichondrium - connective tissues that surround cartilage, provides nutritional support, and protects and regenerates cartilage.

Primary cells are chondrocytes which are found in a space called a lacunae.

Has an extracellular matrix. Collagen fibers resist tension. Has ground substance with watery-gel-like consistency which helps to resist compression.

It is avascular and lacks innervation. Receives nutrients via diffusion. Movement helps nutrients diffuse through the ground substance.

Hyaline (Type II Collagen)

Most abundant type of cartilage. Found in the trachea, nose, and ends of joints.

Contains few collagen fibers (these fibers are not present on micrographs).

Provides. model for the formation of the fetal skeleton.

Provides cushioning between joints.

Elastic (Type III Collagen)

Least common. Contains branched elastic fibers. Elastic fibers are highly flexible and provide elasticity. Found in ear and epiglottis.

Fibrocartilage (Type I Collagen)

Found between slightly mobile bones, such as the pubic symphysis and intervertebral discs.

Provides a cushion between the bones of the knee joint (menisci of the knee).

Resists stretching and compression.

Contain abundant collagen fibers with chondrocytes arranged in parallel.

Bone Functions

1. Support and protection of soft tissue (ex. skull and rib cage).

2. Movement - Muscles anchor onto bone and shorten to produce movement at joints.

3. Energy Metabolism - Some bone cells help regulate blood sugar and fat storage through hormone secretion.

4. Mineral Storage - Holds reserves of calcium and phosphate.

5. Blood Cell Formation (Hematopoiesis) and Energy Storage - Functions that occur in the different types of marrow within bones.

Characteristics of Bone

Made up of cells and extracellular matrix.

Extracellular matrix has both mineralized and organic components.

Hydroxyapatite provides hardness and rigidity to resist compression and organic component

Ground substance and collagen fibers provides flexibility to resist tension.

Cells include osteoblasts (bone forming cells), osteocytes (mature one maintaining cells), and osteoclasts (bone destroying cells).

Flexible and dynamic organics; vascular and innervated; have the capacity to grow, develop, heal and regenerate.

Long Bones

Longer than they are wide.

Humerus, radius, ulna, femur, tibia, fibula, metacarpals, metatarsals & phalanges.

Short Bones

Approximately cube shaped.

Carpals (wrist bones) and tarsals (ankle bones).

Flat Bones

Generally flat and thin.

Neurocranial bones, scapula, and sternum.

Irregular Bones

Have unusual shapes that don't fit into other categories.

Vertebrae, os coxae (hip bones), and facial bones.

Sesamoid Bones

Found within muscle tendons (e.g., patella).

Diaphysis

Shaft of the long bone.

Epiphysis

Ends of the long bones, form joints with other bones. Contains spongy bone.

Medullary Cavity

Space within the shaft of only long bones that contains bone marrow.

Epiphyseal Line

Internal line separating the diaphysis and epiphyses, remnant of the growth plate.

Periosteum

Connective tissue that lines the outside of bone (does not cover epiphyses which are lined by articular cartilage).

Endosteum

Connective tissue that lines the inside of bone including the medullary cavity and central canals.

Compact Bone

Also known as dense or cortical bone, forms the outer surface of bones and is composed of rings of bone surrounding a central Haversian canal.

The canal allows for the passage of nerves and blood vessels through the bone.

Each canal and surrounding ring is called a Haversian system or osteon. These run parallel to and along the entire length of the bone.

Haversian (Central) Canal

Opening through the core of the osteon.

Lacunae

Small spaces in the bone matrix where osteocytes live.

Lamellae

Rings of bone matrix surrounding the central canal (similar to rings of a tree).

Canaliculi

Small channels connecting lacunae to allow osteocytes to communicate.

Volkmann's (Perforating) Canals

Passageways connecting central canals.

Spongy Bone

Also called trabecular or cancellous bone, it is located inside bones and has a mesh or lattice-like appearance.

It is not soft.

Trabecular organize along lines of stress to strengthen bone.

Interstitial Growth

Growth in length; occurs during childhood and adolescence.

Growth in length occurs at a growth plate made of hyaline cartilage that sits between the diaphysis and epiphyses.

Results in increased stature or height through the end of adolescence.

Growth stops when growth plate ossifies and the diaphysis and epiphyses fuse together.

A remnant of the growth plate remains as the epiphyseal plate.

Appositional Growth

Growth in diameter of bone. Can continue to occur throughout life as remodeling occurs.

Osteoblasts secrete bone matrix underneath the periosteum to form new rings (lamellae) of matrix around the bone.

This new bone matrix is then broken down and replaced as cylindrical osteons.

Osteoclasts remove bone matrix inside the bone to increase the size of the medullary cavity.

Bone Remodeling

Ongoing replacement of old bone tissue by new bone tissue.

Occurs to maintain fluid concentrations of calcium and phosphate in the body.

Also occurs to respond and strengthen the bone to resist mechanical stress.

A coordinated process occurring between osteoclasts and osteoblasts, breaking down bone and depositing new bone matrix. Coordination is important to maintain a constant overall bone mass.

Osteoporosis

Low bone mass and a deterioration of the microscopic architecture of the bony skeleton.

Bone respiration outpaces bone deposition with an elevated number of osteoclasts.

Due to loss of bone mass, fractures are common in bones that support most of the body weight such as the neck of the femur and vertebrae.

Occurs most commonly in older females who have gone through menopause with estrogen deficiency as estrogen help maintain bone density.

If there is a hole or opening in a bone, if it is round:

It is a foramen.

If there is a hole or opening in a bone, if it is slit-like:

It is a fissure.

If there is a hole or opening in a bone, if tube-like:

It is a canal or meatus.

If there is a hole or opening in a bone, if a hollow space:

It is a cavity or sinus.

If there is a ridge on a bone, if extensive:

It is a crest.

If there is a ridge on a bone, if it is thin:

It is a line.

If there is a projection on a bone, if it is large:

It is a trochanter, tuberosity, or malleolus.

If there is a projection on a bone, if it is small:

It is a tubercle or process.

If there is a projection on a bone, if it is pointed or spear-like:

It is a spinous process or styloid process.

If there is a depression in a bone, if it is larger and deeper:

It is a fossa.

If there is a depression in a bone, if half-moon shaped:

It may be called a notch.

If there is a depression in a bone, if it is long:

It may be called a sulcus or groove.

When one bone articulates with another capped with hyaline cartilage, if rounded:

It is called a condyle or head.

Human Skeleton

Composed of 206 named bones that can be divided into axial and appendicular groups.

Axial Skeleton

Forms the central axis of the body.

Includes: skull bones, auditory ossicles, teeth, hyoid, vertebrae, sacrum, coccyx, ribs, and sternum.

Skull Bones

29 bones.

Vertebral Column

26 bones.

Thoracic Cage

25 bones.

Upper Limbs

64 bones.

Lower Limbs

62 bones.

Neurocranial Bones

Frontal, parietal, temporal, occipital, sphenoid, and ethmoid bones.

Frontal Bone

Bone of the forehead.

Unpaired.

Supraorbital Foramen (or notch)

Frontal Bone.

Passageway for nerves and vessels above the orbit.

Sometimes it is a hole, sometimes it just looks like a notch.

Superciliary Arch

Frontal Bone.

Bony arch above the orbit.

Parietal Bone

The paired bones form the superior and lateral portions of the neurocranium.

Paired.

Temporal Bone

Has a flat part along the lateral side of the cranium (near the external ear) and another part that forms a section of the cranial base which holds the inner and middle ear structures.

Paired.

Mastoid Process

Bony projection for attachment of muscles.

Styloid Process

Thin bony projection for attachment of muscles.

External Acoustic (Auditory) Meatus

Canal through temporal bone for vibrations in air to travel to contact tympanic membrane (ear drum).

Mandibular Fossa

Depression in bone, articulation site for mandibular condyle (of the mandible) to form the temporomandibular joint (TMJ or jaw joint)

Petrous Portion

The internal part of the temporal bone which contains the middle and inner ear structures (best viewed within the cranial cavity).

Internal Acoustic (Auditory) Meatus

Passageway through the petrous portion of the temporal bone. This is how nerves from the brain access hearing and balance related structures (viewed within cranial cavity).

Jugular Foramen

Passageway formed at the junction of the temporal and occipital bones. Passageway for cranial nerves and blood leaving cranial cavity (viewed within cranial cavity or from cranial base).

Occipital Bone

Forms the posterior and part of the inferior portions of the neurocranium.

Foramen Magnum

Large opening in the base of the skull for the passage of the spinal cord.

Occipital Condyles

Smooth surfaces for articulation with first cervical vertebrae (atlas).

External Occipital Protuberance

Bump of bone along the posterior, midline of the occipital bone. A site for muscle attachment.

Sphenoid Bone

Sits between the face and neurocranium.

Unpaired.

Greater Wing

Larger lateral projections of the sphenoid bone.

Lesser Wing

Flat, superior portions of the sphenoid bone.

Sella turcica

Means "Turkish saddle." Saddle-shaped depression where the pituitary gland sits.

Pterygoid Process

Inferior projection consisting of 2 plates from the bottom of the sphenoid bone.

Optic Canal

Passageway located where the lesser wing meets the body of the sphenoid bone, allows passage of the optic nerve to the eye (viewed within cranial cavity or within orbit).

Foramen Ovale

Opening lateral to sella turcica for the passage of mandibular nerve (viewed within cranial cavity or from cranial base).

Ethmoid Bone

Located anterior to the sphenoid bone and between the orbits.

Unpaired.

Crista Galli

Means "rooster's crest or comb". Superior projection into cranial cavity.

Perpendicular Plate

Inferior projection that forms the superior part of the nasal septum.

Lateral Masses

Lateral projections of the ethmoid bone, contain hollow spaces that are the ethmoid sinuses (or air cells).

Olfactory Foramina

Many small openings around Crista Galli. Passageway for olfactory nerves to enter the nasal cavity (viewed within cranial cavity).

Suture

Fibrous joints between neurocranial bones that allow for virtually no movement between bones.

Coronal Suture

Between parietal and frontal bones.

Sagittal Suture

Between left and right parietal bones.

Lambdoid Suture

Between parietal and occipital bones.

Squamosal Suture

Between parietal and temporal bones.

Fontanelles

Soft spots between neurocranial bones of an infant's skull where they have not yet fused together.

Bones are connected by membranes which are soft and later replaced by bone tissue.

They allow for more skull growth during infancy and flexibility during birth.

Vomer

Vertical plate that forms the inferior part of the nasal septum.

Unpaired.

Nasal Septum

Divides the left and right spaces of the nasal cavity. It is made of cartilage anteriorly (septal cartilage) and bone posteriorly. The bony part of the septum is formed by the perpendicular plate of the ethmoid bone and vomer.

Maxilla

Upper jaw bone.

Paired.

Infraorbital foramen

Opening below the orbit for nerves and blood vessels to pass onto the face.

Palatine Bones

Located posterior to the maxillary bones (or maxillae). These bones articulate with the maxillae to form the hard palate.

Cleft Lip and/or Palate

Failure of the left and right palatine or maxillae to fuse together.

Zygomatic Bone

Cheek bone.

Paired.

Zygomatic Arch

Projections from the zygomatic and temporal bones articulate to form the zygomatic arch.

Nasal Bones

Form the bridge of the nose.

Paired.

Lacrimal Bones

Bones at the corner of each eye that cradle the tear ducts.

Paired.

Nasolacrimal Duct

Passageway from the lacrimal bone (orbit) to the nasal cavity for the drainage of tears.

Mandible

Lower jaw bone.

Unpaired.

Ramus

Vertical portion of the mandible.

Corpus (Body)

Horizontal part of the mandible that holds the teeth.

Mandibular Condyle

Posterior projection from the ramus that articulates with the mandibular fossa of the temporal bone to form the temporomandibular joint.