Nervous system : Difference between tract and nerve

Composition of nervous tissue :
1. neuron : excitable cell
2. Neuroglia : supporting cells
Parts of a neuron :

1. cell body 
2. processes : 2 in number 

i) dendrite: 1 or more than one in number

ii) Axon : usually one in number 

Axons are situated both CNS PNS
axon within the CNS is known as tract 
axons outside the CNS is known as nerve 

Topic                              Tract                                                 Nerve
location                          Mostly CNS                                   Part of PNS (peripheral NS)
myalination                     oligodendrocyte                           Schwann cells 
Type                   Ascending & descending tract    Sensory, motor and mixed both sensory& motor

Connective tissue composition: easy brief explaination

The main components of connective tissue is  cells (different types of cells with different functions)
Cells of connective tissue produce fibres (protein ) and ground substance ( a protein - carbohydrate composition )

Cells of connective tissue are two types

Connective tissue fibers are formed within connective tissues cells(fibroblast) ,
after formation they leave the cells and
become part of extra cellular matrix
collagen and reticular fibres are formed by collagen proteins 
elastic fibres are formed by elastin protein 

Ground subtances also secretion of connective tissue cells
They are nothing but a protein-carbohydrate complex
they consists of
1. proteoglycans
2. Glycosaminoglycans
3. Glycoprotein

easy and brief difference between tissues

Tissue means
group of cells and their extra cellular matrix ,
They do specific function or functions
Tissue : 4 types
1. epithelial tissue
2. connective tissue
3. muscular tissue
4. nervous tissue
Features of tissues :
Tissue                                     Cells                          extra-cellular matrix 
epithelium                        large number of cell                little
connective                        small number of tissue            large amount
muscular                           specialized cells                       moderate in amount
nervous                            neuron & neuroglia                  no extra cellular matrix

What is grey matter and white matter ?

One of the important  and vital questions of nervous system:
what is grey and white matter ?
Before explaining this we need to know about a neuron
  A neuron has two part
cell body and
processes : dendrites and an axon

if we arrange several neuron in single layer like following picture, we see cell body of neuron make a layer and processes of neuron makes a layer
Both this layer contain neuroglia and blood vessels

So, composition of grey and white matter is : 

•Gray matter:  Neuron cell  bodies

                            Neuroglial cells

                            Blood vessels

•White matter:  Processes  of neuron

                             Neuroglial cells

                             Blood vessels

Location of gray & white matter in the CNS

•Cerebrum and cerebellum ,

•Outer gray matter

•Inner white matter

•Spinal cord,

•outer part white matter

•Inner gray matter

  Why location of grey and white matter differ in different parts of CNS.

Glandular epithelium is developed from covering epithelium

Mechanism of formation of exocrine glands from covering epithelium
epithelial tissue broadly classify into two group
1. covering epithelium
2. glandular epithelium
Glandular epithelium with duct is known as exocrine glands
Glandular epithelium without duct is known as endocrine glands
Both exocrine and endocrine glands are developed from covering epithelium
exocrine glands remain their contact with covering epithelium but endocrine glands lost the contact .

Gastrointestinal tract related with different exocrine glands.
in generally, there are four histological layers of gastrointestinal tract
1. mucosa : is formed by  three layers
a) lining epithelium
b) lamina propria : connective tissue
c) muscularis mucosae: smooth muscle cells
2. submucosa : connective tissue
3. muscles layer: smooth muscle cells
4. serosa : formed by connective tissue and simple squamous epithelium (mesothelium)
From the lining epithelium of gastrointestinal tract glandular epithelium begin to form
some exocrine gland enter into lamina propria ex: gastric glands, intestinal gland etc
some are enter into submucosa ex: Brunner;s gland
some are go out side of gut wall ex: liver, pancreas
So, all glandular epithelium is originate from covering epithelium

Classification of epithelium

Classification of epithelium 

Atlanto‐occipital joint

Type: ‐ Synovial joint of Ellipsoid variety

 Articular surface‐

• Above: convex occipital condyles

• Below: Concave superior articular facet of  atlas

       Important relation of atlas: Inferolateral free margin of altas arches over the vertebral artery and first cervical nerve

•       Blood supply: Vertebral artery

•       Nerve supply of joint:  C1 nerve

•       Movements of joint:

•       • Ellipsoid joint ( biaxial joint)

•       • Flexion / extension (nodding)‐ transverse axis

•       • Lateral flexion‐ antero-posterior axis

•       The atlantoaxial joint :

•       is a joint in the upper part of the neck between the first and second cervical vertebrae; the atlas and axis.

•       The atlantoaxial joint is of a complicated nature. It consists of three joint:

•       Comprise of

•       A pair of lateral atlantoaxial joints: (Plane joint) between inferior facets of atlas and superior facets of axis.

•        A median atlanto-axial joint: (pivot joint) between the dens and anterior arch and transverse ligament of atlas

•       Movements:

•        All three joints produce rotatory movement around a vertical axis (No movement)

•        Movement is limited by alar ligament

•        Muscles producing movement are: Rectus capitis posterior major, obliquis capitis inferior, splenius capitis of one side along with sternomastoid of other side

(The median atlantoaxial joint is sometimes considered a double joint:

•       one between the posterior surface of the anterior arch of atlas and the front of the odontoid process

•       one between the anterior surface of the ligament and the back of the odontoid process)  

The ligaments connecting these bones are:

1. Articular capsules
2. Anterior atlantoaxial ligament
3. Posterior atlantoaxial ligament
4. Transverse ligament of the atlas