Cartilage, Bone, Nervous System

Cartilage

A tough, resilient connective tissue whose cells are surrounded by a large ECM

Chondroblast

Developing cartilage cell that produces cartilage matrix

Chondrocyte

Mature cartilage cell located in a lacuna

Lacuna

A small space in the cartilage matrix containing a chondrocyte

Perichondrium

Dense connective tissue surrounding most cartilage

Hyaline Cartilage

Cartilage with a glassy ECM rich in type II collagen and aggrecan

Elastic Cartilage

Cartilage containing elastic fibers that provide flexibility

Fibrocartilage

Cartilage combining cartilage matrix with dense connective tissue rich in type I collagen

Hyaline Cartilage

This provides a low-friction surface, participates in lubricating synovial joints, and distributes applied forces to the underlying bone

Isogenous Group

A group of chondrocytes produced by division of a cartilage cell

Interstitial Growth

Cartilage growth caused by cell division within the existing matrix

Appositional Growth

Cartilage growth caused by new cells being added at the periphery

Avascular Cartilage

Cartilage lacks blood vessels, which contributes to its slow repair

1. Respiratory Tract

2. Articular surfaces

3. Epiphyseal Plates

4. Fetal Skeleton

Hyaline cartilage locations:

1. External Ear

2. Auditory Tube

3. Epiglottis

4. Parts of the Larynx

Elastic cartilage locations:

1. Intervertebral Discs

2. Pubic Symphysis

3. Menisci

4. Some tendon insertions

Fibrocartilage locations:

Hyaline Cartilage

This cartilage provides smooth support

Elastic Cartilage

This cartilage provides flexible support

Fibrocartilage

This cartilage provides strong resistance to compression and tearing

Articular Cartilage

Hyaline cartilage that covers the articular surfaces of tip of joints

Articular Cartilage

This cartilage has no perichondrium

Articular Cartilage

Is a remnant of the original hyaline cartilage template of the developing bone, and it persists throughout adult life

Osteoarthritis

Most common form of arthritis; characterized by the breakdown of cartilage and underlying bone, leading to pain, stiffness, and decreased mobility

Bone

A connective tissue with a calcified ECM that supports and protects the body and serves as a calcium reservoir

Bone Tissue

Is the structural component of bones

Bone Tissue

Is a specialized connective tissue composed of calcified extracellular material, bone matrix, and bone cells

Osteoprogenitor Cell

A precursor cell that can differentiate into an osteoblast

Osteoblast

Bone-forming cell that produces osteoid

Osteoid

Newly produced, unmineralized bone matrix

Osteocyte

Mature bone cell enclosed within bone matrix that maintains the matrix and senses mechanical stress

Osteoclast

Large bone-resorbing cell formed by fusion of monocyte-derived cells

Lacuna

Space in the bone matrix containing an osteocyte

Canaliculi

Tiny channels connecting lacunae and allowing communication between osteocytes

Hydroxyapatite

Calcium phosphate crystals responsible for the mineral hardness of bone

Periosteum

Dense connective tissue covering the external surface of bone

1. Fibrous Layer

2. Osteogenic Layer

The periosteum consist of 2 layers:

Fibrous Layer

Outer layer of dense connective tissue containing mostly bunded type I collagen, but also fibroblast and blood vessels

Sharpey's Fibers

Perforating fibers, bundles of periosteal collagen that penetrate the bone matrix and bind the periosteum to the bone

Osteogenic Layer

More cellular inner layer which includes osteoblasts, bone lining cells, and mesenchymal stem cells referred to as osteoprogenitor cells

Endosteum

Thin cellular layer lining internal surfaces of bone

1. Compact Bone

2. Spongy Bone

Bone tissue is classified as either:

Compact Bone

Dense bone forming much of the outer portion of bones

Cancellous Bone

Spongy bone composed of interconnected trabeculae

Trabecula

Thin structural element of cancellous bone

Osteon

Structural unit of compact bone consisting of concentric lamellae around a central canal

Woven Bone

Immature bone with randomly arranged collagen

Lamellar Bone

Mature bone with organized layers of collagen

Intramembranous Ossification

Bone formation directly from mesenchymal tissue

Endochondral Ossification

Bone formation in which a cartilage model is gradually replaced by bone

Bone remodeling

Continuous removal and replacement of bone matrix

Bone Repair

Bone is vascularized which gives it a good ability to repair itself

Appositional Bone Growth

Increase in bone thickness through addition of new bone at its surface

Bone Cavities

A thin lining that internally covers small trabeculae of bony matrix that project into the marrow cavities and lines the bone marrow

Long Bones

Are longer in one dimension than other bones and consist of a shaft and two ends (e.g., the tibia and the metacarpals)

Short Bones

Are nearly equal in length and diameter (e.g., the carpal bones of the hand)

Flat Bones

Are thin and plate-like (e.g., the bones of the calvaria [skull cap] and the sternum). They consist of two layers of relatively thick compact bone with an intervening layer of spongy bone

Irregular Bones

Have a shape that does not fit into any of the three groups just describes; the shape may be complex, or the bone may contain air spaces or sinuses

50%

Inorganic material represents about ___ of the dry weight of bone matrix

Calcium Hydroxyapatite

Is the most abundant, but bicarbonate, citrate, magnesium, potassium, and sodium ions are also found

Ossification

Process which includes both secretion of organic matrix by bone cells and its subsequent calcification; or may only refer to secretion of organic matrix

Intramembranous Ossification

Formation of bones directly from mesenchymal connecctive tissue

Endochondral Ossification

Formation of bone within pre-existing cartilage model

Parathyroid Hormone

Released by the parathyroid glands

Parathyroid Hormone

Raises low blood calcium levels by stimulating osteoclasts and osteocytes to resorb bone matrix and release Ca2+ to the blood

Calcitonin

Produced by the thyroid gland

Calcitonin

Can reduce elevated blood calcium levels by opposing the effects of the PTH in bone

Osteoporosis

Is a health condition that weakens bones, making them fragile and more likely to break - causing a risk for fractures

Osteoporosis

Develops when bone mineral density and bone mass decreases, or when the structure and strength of bone changes

Nervous Tissue

Tissue specialized for communication through electrical and chemical signals

Neuron

The main functional cell responsible for receiving, processing, and transmitting nervous signals

1. Golgi Type I

2. Golgi Type II

Neurons can be classified based on the length of their axons:

Golgi Type I

With long axons

Golgi Type II

With short axons

1. Central Nervous System

2. Peripheral Nervous System

The nervous system has two major anatomical divisions:

1. Somatic Nervous System

2. Peripheral Nervous System

The peripheral nervous system is classified into:

1. Sympathetic

2. Parasympathetic

3. Enteric

The autonomic nervous system is classified into:

Cell Body, Soma, or Perikaryon

Main part of the neuron containing the nucleus and most organelles

Dendrite

Neuronal process specialized mainly for receiving signals

Axon

Neuronal process that conducts signals away from the cell body

Axon Hillock

Region where the axon begins and where action potentials are commonly initiated

Myelin Sheath

Lipid-rich covering around certain axons that increases the speed of impulse conduction

Nodes of Ranvier

Gap between adjacent myelin segments where ion exchange occurs during saltatory conductions

Neuroglia or Glia

Supporting cells of nervous tissue

1. Ependymal Cells

2. Astrocytes/Astroglia

3. Oligodendrocytes/Oligoglia

4. Microglia/Mesoglia

Neuroglia:

Oligodendrocyte

CNS glial cell that forms myelin around portions of multiple axons

Interfascicular Glia

Type of oligoglia found arranged in rows or columns along nerve fiber in the white matter

Schwann Cell

PNS glial cell that forms myelin around a segment of one axon

Astrocyte

CNS glial cell that supports neurons, regulates the extracellular environment, interacts with blood vessels, and contribute to the blood-brain barrier

1. Fibrous Astrocytes

2. Protoplasmic Astrocytes

Subtypes of astrocytes/astroglia:

Fibrous Astrocytes

Processes are smooth, thin, with few branches; most numerous in the white matter

Protoplasmic Astrocytes

With numerous freely branching thick processes with granular cytoplasm; most numerous in gray matter

Glisomes

Small granular swelling along the processes of astroglia, representing clumps of mitochondria

Microglial Cell

CNS immune-related glial cell with phagocytic functions

Ependymal Cell

Cell lining the ventricles of the brain and central canal of the spinal cord

Satellite Cell

PNS glial cell surrounding and supporting neuronal cell bodies in ganglia

Capsule Cells

Flattened cells forming a continuous capsule around nerve cell bodies in the ganglion

Blood-brain barrier

Specialize barrier that regulates movement of substances between blood and CNS tissue

Synapse

Specialized site where a neuron communicates with another cell

1. Axodendritic

2. Axosomatic

3. Axo-axonic

Synapses can be morphologically classified into:

Myelin Sheath

Surrounds the axon from the surrounding extracellular compartment of endoneurium