Dermatology Made Simple : Structure and Function of the Skin

Structure and functions of the skin

Skin structure

The skin is the largest organ of the body. It has three main layers, the epidermis, the dermis and the subcutaneous layer.

The epidermis is an elastic layer on the outside that is continually being regenerated. It includes the following:

• Keratinocytes - the main cells of the epidermis formed by cell division at its base. New cells continually move towards the surface. As they move they gradually die and become flattened.

• Corneocytes - the flattened dead keratinocytes that together make up the very outer layer of the epidermis is called the stratum corneum or horny layer. This protective layer is continually worn away or shed.

• Melanocytes – produce the pigment melanin that protects against UV radiation and gives skin its colour.

• Sweat glands – produce sweat that travels via sweat ducts to openings in the epidermis called pores. They play a role in temperature regulation.

• Hair follicles – are pits in which hairs grow. Hairs also play a role in temperature regulation.

• Sebaceous glands – produce sebum (an oil) to keep hairs free from dust and bacteria. Sebum and sweat make up the ‘surface film’.

The dermis is the inner layer that includes the following:

The subcutaneous layer under the dermis is made up of connective tissue and fat (a good insulator).

Functions of the skin :

• Provides a protective barrier against mechanical, thermal and physical injury and hazardous substances.

• Prevents loss of moisture.

• Reduces harmful effects of UV radiation.

• Acts as a sensory organ (touch, detects temperature).

• Helps regulate temperature.

• An immune organ to detect infections etc.

• Production of vitamin D.

Dermatology Made Simple : Introduction to blistering disorders of the skin

Introduction to blistering disorders of the skin

Blisters arise due to separation of epidermal cells as a result of one of the following phenomenon:

Allergic  reaction

Trauma or injury

Infection

Oedema

Inflammation

Vasculitis

In addition,allergy causes immune reactions that ocuur at junction of epidermis and dermis aand cause blister formation.

Predisposing Factors:

There is a high chance of blister formation in indivduals with predisposition to allergy and there is an element of genetic susceptibility as well.

Most common blistering disorders of the skin (also known as immunobullous disorders are as follows:

Pemphigoid

Pemphigus

Dermatitis Herpetiformis

Linear IgA

General Principles Of Management :

Avoid precipitans

Topical treatment

Systemic Therapy including immunosuppressive drugs

Skin Blister

Computer Studies Made Simple : Network Topology

Network Topology

This term refers to the physical layout of connected devices in  a computer network .

It explains the locations of various computers in a network.

Types of Network Topologies:

Bus topology

Mesh Topology

Star Topology

Tree topology

Ring Topology


Bus Topology:

This is most simplest type of network

Its Is good for a network with small number of computers.

All computers in this network are connected to one common communication medium.

This medium Is called as BUS and is usally a central wire

Terminators are used at end of the BUS to absorb signals.

If two computers transmit data at the same time,a collision can take place.

This type of topology is mostly used in Peer to Peer Networks.

If a  computer  wants to send data to another computer in the network,it will do so via the bus.

The data and address move from one computer to another.

Each computer will check the address.If this matches with address of the computer,the computer will keep
the data.If not,the data will move on to the next computer.

Advantages:

1.It is simple to use

2.It is economical in terms of its costs.

3.Even if there is failure of one node,it will not affect working of rest of the network.

4.It is easy to add more computers to this network by extending the bus.

5.The amount of cable use is not much and thus is very cheap and easy to use.

Disadvantages:

1.Only a small number of computers are supported bythis network.

2.In case of an error in network,it is difficult to trouble shoot.

3.If more computers are added to this network,the network speed and efficiency will decrease.

Dermatology Made Simple : Benign Skin Tumors

Benign Skin Tumors

Seborrhoeic Warts:

They are usually found on face,trunk and neck.

Their size varies from as small as 0.3 cm to upto 4 cm.

They may have variable color varying from light brown to dark brown.

They may or may not have a peduncle (pedunculated or non-pedunculated respectively).

Dermatofibroma:

These are small nodules that arise in the dermis.

Their colour varies from red to light brown.

They are usually seen in women.

They are usually found on legs

Predisposing Factor:

It is believed they are mostly seen in areas of skin that are exposed to trauma.

  Dermatofibroma

Skin Tags:

They are usually seen at places where skin can get rubbed by skin or clothing.

They are found in axillae,neck,groin and under breasts.

They may be pigmented and color varies from light brown to dark brown.

Computer Studies Made Simple : Computer Network Standards

Network Standards:

These refer to the rules and regulations that reflect the technical and physical specifications about a computer network.

Types of Network Standards:

There are two main types of network standards:

1.De Facto

2.De Jure

1.De facto:

These standards have developed over course of time with historical developments and are based on research and experience.

These are mostly used by organizations.

2.De Jure:

These standards have been devised by governing bodies in networks.

These are a set of protocols devised by major organizations.

Some of organizations that design these regulations are as follows:

IEEE : Institute of Electrical and Electronics Engineers

IEA : The Electronic Industries Association

ANSI : American National Standard Institute

Computer Studies Made Simple : Peer to Peer Model

Peer to Peer Model

In this type of computer model,all computers operate individually and have equal status

There is no computer that acts as server.

Each computer has got access to files and data on other computers in the network.

This model  has the disadvantage of being less secure as the data is stored on more than one computer in the network and hence is prone to damage or loss.

Also it is slower than the client server network.

Hybrid Models:

These models include both Client Server Models and Peer to Peer models and hence have properties and advantages of both these models.

Dermatology Made Simple : Changes in Nails in Systemic Disease 2

Onycholysis:

This term is used to describe detachment of nail from its nail bed.

Causes:

Mechanical causes

Manual trauma

Systemic Diseases:

Thyrotoxicosis

Psoriasis

 Onycholysis

Pitting:

This refers to small pits or depressions on nail surface

Causes

It is usually associated with several systemic disease such as:

Psoriaisis

Alopecia areata

Lichen planus

 Nail Pitting

Thickening of Nails:

These can occur in a variety of conditions:

Chronic nail trauma

Fungal infections

Psoriasis

Leuconychia:

This means the color of nails is white.

It is seen with low protein states such as Hypoalbuminemia and 

Liver diseases causing cirrhosis of Liver

 Leuconychia of nails