Covering epithelium: simple epithelium

 There are two logic in classification of covering epithelium
1st : arrangement of cells :
single cellular layer known as simple epithelium

Multiple cellular layer known as stratified epithelium

2nd logic : shape of cells
There are three types of cells
flat cells : squamous
cuboidal cells
columnar cells

so, you can make three types of simple epithelium
1. simple squamous epithelium
2. simple cuboidal epithelium
3. simple columar epithelium
Another simple epithelium is pseudo-stratified ciliated columnar epithelium
Pseudo means false
it looks like multilayered epithelium but it is a simple epithelium
cells are arranged in single layer but size of cell different
some are tall
some are short
 Location of nuclei of cells are in different position so it looks like multilayer epithelium but it is nothing but simple epithelium

finally we find four typres of simple covering epithelium

Histological layers within a vessel: easy discussion

  Vessel (artery, vein) : vessels are tube like structure. 

Histologically there are three district layers within outward.

1. Tunica intima : the inner most layer. it is the combination of three layer

• endothelium : simple squamous epithelium
• subendothelial connective tissue: a very thin connective tissue layer occasionally contain smooth muscle cells 
• internal elastic lamina : a membrane like structure which is formed by elastic fibres

  2.Tunica media :it is formed by

• smooth muscle cells : number of cell layer vary in large, medium and small sized artery and vein 

• elastic and collagen fibres 

3. Tunica adventitia : this layer is formed by connective tissue rich in collagen fibers. The thickness of this layer also vary in artery and vein

some time external elastic lamina separate tunica media from tunica adventitia

Typical synovial joint : easy discussion about features

Synovial joint:

 is the most common joint in the body 

Minimum to Wide range of movement is one of the important features of synovial joint

why synovial joint moves but other joints (like fibrous and cartilaginous) movement are restricted ?

Joint means articulation or junction between two or more bone,
in synovial joint bones are separated by a joint cavity 
This joint cavity are responsible for wide range of movement 
So joint cavity is the unique character of a synovial joint 

Classification of capillary : easy explaination

Capillary: it is the smallest part of blood vascular system.

Formation : it is formed by endothelium (simple squamous epithelium) with their basement membrane.

Classification of capillary: 
to do specific function structure of capillary is changed.
there are three types of capillary :
1. continuous capillary:
  endothelium and basement membrane are continous. there are no gap between endothelium and basement membrane is also formed a continuous layer . This type of capillary found in special area of body. Like brain, where it formed blood brain barrier. exchange between blood and brain tissue are highly selective so, this continuous capillary act as barrier. For this selective materials enter into brain by diffusion crossing endothelium and its basement membrane.

2. Discontinuous capillary: endothelium and basement membrane are discontinous.
there are  gap between endothelium.
different areas of basement membrane is also discontinuous.
This type of capillary found in some area of body where rapid exchange of nutrient ions are required
Using these gaps exchange of nutrient ions easily occurred between blood and selective tissues of body.
Like liver, spleen

3. Fenestrated capillary :   endothelium and basement membrane are continous.
there are no gap between endothelium.
basement membrane is also formed a continuous layer .
Why it is  known as fenestrated capillary ? 
Fenestration means tiny hole. these holes are present within an endothelium. Like holes within a leaf . just an example, a leaf (considered as endothelium) and tiny holes within it consider as fenetre

e

there are two types of fenetrated capillary
i) fenestrated capillarty with diaphragm

ii) fenestrated capillary without diaphragm

What is diaphragm?
it is a ultra thin membrane which covers fenestra
This type of capillary found in special area of body.
The fenestrated capillary without diaphragm  found in kidney glomerulus
this capillary takes part in formation of filtration apparatus so, exchange of materials done through fenestra
Fenestrated capillary with diaphragm found in other areas of kindey except glomerulus.
exchange of materials is occurred through ultra  thin   membrane of diaphragm

Skelatal Muscle : easy general features

Muscle: is one of the basic tissue contain
specialized contractile cells with
moderate amount of connective tissue
Muscle means 'mouse like' structure

Muscles are three types:
skeletal muscle
cardiac muscle
smooth muscle
skeletal muscle: this type of muscle attached with bones (skeleton) 
Parts : each muscle has two part

Fleshy part : formed by  skeletal muscle cell (muscle fibre) .the direction of muscle fiber vary cell to cell
Fibrous part:
tendon : dense regular connective tissue. usually cylindrical in shape  
Aponeurosis : connective tissue membrane ( dense regular connective tissue) 

 each  skeletal muscle has two or more attachment site 
origin : also known as proximal attachment. Attachment nearer to trunk
insertion :  also known as distal attachment. Attachment away from  trunk

Two attachment, origin and insertion never occurs  in same bone 

each muscle of body must cross a joint or joints.

This muscle responsible for the movement of this joint 

Tissue preparation for making histological slides: easy & short discussion

Tissue preparation

Under the light microscope, tissues are examined via a light beam that is transmitted through the tissue. But the tissue and organs are usually too thick for light to pass through them. For this region tissues have to sectioned to obtain thin, translucent sections. Before making the histological slide tissue has to pass though some preparation processes. Following are the steps of tissue preparations of histological slide.

Steps of tissue preparation for study 

1. Selecting parts of tissue: part of an organ selected and cut. The best thickness are 3-5mm

2. Fixation: The process of avoiding tissue damage from bacteria or autolysis (cell digestion by cells own enzymes) by the help of some chemicals (fixatives) is called fixative.

Name of fixatives: Formaline: Formaldehyde  is a gaseous substance but 40% of it soluble in water. In tissue prepation we uses  :10% formaldehyde(CH20) solution in water.

• Uses of formalin: used as a disinfectant or to preserve biological specimens.

•  Health hazards: short time exposure:  irritation of eye,skin, mucosa of nose and throat, it is  carcinogenic substance  but not teratogenic.
• Precurtion during use of formalin :
•  Exposure to mild formalin for 8 hrs /per day or 40 hrs in a week is safe. Formalin is not absorbed through skin so mild formalin can be handling for short time. After handling wash hand with soap and plenty of water for few min. For long term handling use gloves. Contamination of eye with formalin: wash eye with water for 15 min and consult with ophthalmologist.

Dehydration : after fixation, tissue must be dehydrate by graded series of ethanol and water, usually from the 70% to 100% 

Clearing : after dehydration, tissue must be clean with xylene.

3. Infiltration: after clearing  tissue must be infiltrate with paraffin.

 What is paraffin: for infiltration, tissue must place into a container containing liquid paraffin and place it  in an incubator at the temperature of 58-60 C 

4. After that tissue must be place in a cash for embedding or block formation
5. then sectioning with microtome : now block of the tissue cut by microtome ( a cutting instrument ) 

Paraffin block :Tissue within it  

Microtome machine

Thin section of tissue

 Removing extra paraffin from tissue section & picking up tissue on glass slide for staining 

4. Staining: unfortunately tissues are colourless can not be observe in microscope. So need to be stain. For staining rehydration is necessary. Rehydration is done by graded ethanol and water from 100% to 70%.
5. In routine staining hematoxilin and eosin

Name of the staining and its components:

Basophilic : Tissue components that stain more with basic dye is called basophilic

Acidophilia : tissue components that stain more with acidic dye is called acidophilic

Colour of different components of tissue by hematoxilic and eosin staining :
Hematoxylin is a dark blue or violet stain that is basic/positive. It binds to basophilic substances (such DNA/RNA - which are acidic and negatively charged).
DNA/RNA in the nucleus, and RNA in ribosomes in the rough endoplasmic reticulum are both acidic because the nucleic acid building blocks that come off the phosphate backbone are negatively charged. These form salts with basic dyes containing positive charges. Therefore, dyes like hematoxylin will bind to them and stain them violet.
Eosin is a red or pink stain that is Acidic / Negative. It binds to acidophilic substances (such as proteins - which are basic and positively charged).

6. Dehydration: after staining tissue need to be dehydrate again for long preservation.

7. Clearing: after dehydration tissue need to be clean with xylene. 
8. Amounting: DPX. This chemical place above the tissue and covered by coverslip for long term use.

Now a histological slide is ready for study. 

Choroid plexus : easy understanding and important information

1. Choroid plexus:

these structure situated withing the ventricle of brain 

Formation: 

1. Ependymal cells (cells of ventricles of brain, simple cuboidal epithelium) 
2. capillary 
3. pia mater (inner most layer of meninges
   

Location :  

1. two lateral ventricles 
2. 3rd ventricle
3. 4th ventricle 

Choroid plexus absent in :

1. frontal and occipital horn of lateral ventricles 
2. cerebral aqueduct 

Functions :

1. it produce cerebrospinal fluid 
2. it forms blood CSF barrier
3. it maintain extracellular milieu throughout the brain and spinal cord 
4. it provide nutrition and remove waste product 

Clinical anatomy:

1. choroid plexus cyst: it is found in fetus at early part of development usually disappear later part of development. it produces no effect in growth and development of CNS. some genetic disorder related to this condition like down's syndrome and Edward syndrome 
2. Choroid plexus fails to function properly with age so it contribute the clinical condition like Alzheimer's disease, multiple sclerosis, Parkinsonism etc.