Know Your Skin in Depth

INTEGUMENTARY SYSTEM (SKIN)

 What is Skin ?

The skin is the outermost covering of the body. It is stretched all over the body in the form f a layer . 

Functions of Skin 

1. Protection 

* It protects the underlying tissues from mechanical shocks 

* It holds the body fluids inside and prevents excess loss of water by evaporation.

* It prevents the entry of harmful substances 

* It protects the body from the harmful ultraviolet radiations 

2. Sensation 

Our skin is a sense organ od touch , pain , pressure and heat 

3. Temperature Regulation 

The skin prevents loss of heat in cold weather and facilitates loss of heat in hot weather. 

4. Storage of food

The skin stores food in the special layer of fat cells.

5. Excretion 

The skin eliminates wastes in the form of sweating 

6. Synthesis of vitamin D 

The skin synthesize vitamin D when exposed to sunshine .

LAYERS OF SKIN 

1. THE EPIDERMIS 

The epidermis is the outermost layer of the skin which we can see through naked eyes everyday.

The upper layer of epidermis consists of a layer of dead cells and the lower layer of epidermis consists of a basement membrane . 

The basement membrane consists of specialised cells called as melanocytes .

These melanocytes divide continuously .

These melanocytes consist of a pigment called melanin.

Melanin is a pigment which imparts colour to your skin.

More the melanin , more the person has a darker skin.

Melanin is the pigment which acts as a sheild and provides protection from the harmful UV rays .

Hence, darker the person, more safer from the ultraviolet radiations and hence less susceptible to skin cancer.

Melanin under extreme sunshine underoes tanning of skin which actually prevents us from harmful UV rays.

Tanning process is stimulated by the hormone MSH (melanocyte stimulating hormone ) which is secreted by Intermediate Pituitary Gland .

The dead cell layer of the epidermis consists of keratinocytes which contains a protein called keratin.

This keratin forms a tough protective layer , hence acts as a natural barrier and prevents entry of many harmful substances.

The epidermis also consists of Langerhan cells which attacks the harmful bacteria and viruses that enter the skin.

The dead cell layer of epidermis sheds and gets replaced after every 20-30 days.

The dead cell layer is the stratum cornuem and and melanin part is stratum basale .

2.THE DERMIS 

Below the epidermis is the dermis layer which is divided into two regions :

1. The upper papillary region 

2. The lower  reticular region 

Upper papillary layer - 

It is made up of loose connective tissue .

Lower reticular layer -

It is made up of tightly packed tissues 

The dermis consists of strong collagen and elastin fibres pierced by blood vessels. 

These blood vessels help to regulate the temperature by increasing the blood flow to the skin when you are hot and constricting the blood vessels when your cold and need to keep calm.

The dermis consists of a network of nerves and receptors which help us to sense touch , feel , pain and pressure.

The dermis consists of skin derivatives such as oil glands or sebaceous glands, hair follicles and sweat glands. 

Dermis also acts as a cushion on an injury. 

 

Skin Derivatives 

The derivatives of skin includes sweat glands, nails, sebaceous glands, nails , hair follicles and mammary glands .

1. SWEAT GLANDS

Sweat glands are a dermal derivative of the skin and are of two types :

a) Eccrine sweat glands                               B) Apocrine sweat glands 

They are present all over the body.                              They are concentrated in the armpits.

The sweat produced by it cools down                          The sweat secreted is slightly thicker and is
the body when temperature rises.                                 milky, which is released during stress.
                                                                                          
                                                                                         The secretions of this gland produces body 
                                                                                          odor which causes the bacteria to multiply 
                                                                                           and their waste gives rise to unpleasant 
                                                                                            smell.
The eccrine glands open up directly into                       Apocrine glands release sweat at the root
skin's epidermis.                                                                of hair follicles. 


 

SEBACEOUS GLANDS (OIL GLANDS)

Sebaceous glands are small oil producing glands . These are attached to the hair follicles and release sebum or oil in thr follicles and then on the surface of the skin. These glands are abundant on the scalp and the face.

The sebum forms a greasy surface which keeps the skin flexible and prevents the loss of large amounts of water. 

These glands are involved in the development of a common adolescent skin disease known as acne. 

HAIR FOLLICLES 

It is a structure of skin from where the hair grows. The hair follicles are all over the body except the lips, palms, and soles. 

The hair follicle has oe or two sebaceous glands which secrete sebum and lubricate the hair follicles. Apocrine glands help in lubricating the hair follicles of the armpits. 

The hair follicle also consists of a errector pilli which is responsible to create goosebumps when contracted. 

The papilla of the hair follicles consist of epithelial cells responsible fr hair growth and melanocytes which are responsible to impart colour to te hair. 






NAILS 

Nails are known as germinal matrix , a tissue lying beneath the skin behind the fingernail.
The matrix consists of nerves and blood vessels and supplied with the nutrients. 





MAMMARY GLANDS

Mammary word comes from the word mammals. The mammary glands are the extensions of the apocrine sweat glands. Mammary glands develop in the females at the time of puberty under the influence of a female sex hormone estrogen. 

The mammary glands are responsible for the secretion of milk for the new born offspring. 

The milk oozes out of the breasts under the influence of hormones prolactin and oxytocin. 

Derivatives of skin 

understanding the importance of breathing every second

RESPIRATORY SYSTEM 

Respiration is a metabolic process common to all living things. It is a biochemical in which the cells of an organism obtain energy by combining oxygen and glucose, resulting in the release of carbon dioxide, water and ATP. 

PARTS OF RESPIRATORY SYSTEM

  The respiratory system consists of nose, pharynx, larynx, trachea, bronchi and finally the lungs. These are together known as air passages. 

1. The Nose -  The nose consists of an external pair of nostrils which is separated by a cartilage known as nasal septum. 

The nostrils open into the nasal chambers. 

The inner part of the nostrils consists of a lining of mucous and hair.

The nasal hair entraps the dust particles and the mucous tra4ps the bacteria and lubricates the nasal tract.

2. The Pharynx -  The nasal chambers open at the back into a wide cavity, the pharynx, situated at the back of the mouth.

It is a common passage for air and food. 

It leads ito an air tube.

The trachea and a food tube located behind the trachea.

The entrance to the trachea is guarded by a flap called epiglottis which closes it at the time of swallowing food. 

Incomplete closure of epiglottis during swallowing causes cough. 

3. The Larynx - The larynx or the voice box is a hollow cartilagenous structure located at the start of windpipe. The larynx consists of vocal cords which produces sound. 

4. The Trachea - The trachea or wind pipe emerges from the larynx down below in the neck where it is partly covered by the thyroid gland . The walls of the trachea are strengthened by C-shaped rings of cartilage .

5. The Bronchi -   The trachea divides into two tubes , called the bronchi , which enter the respective lungs. On entering the lungs each bronchus divides into fine secondary bronchi, which further divides into still finer tertiary bronchi. 
Bronchioles are the subsequent still finer tubes of tertiary bronchi. By repeated branching , the bronchioles ultimately end in a cluster of tiny air chambers called the air sacs or alveoli.

6. The Lungs -  The lungs are a pair of spongy and elastic organs formed by the air sacs, their connecting bronchioles, blood vessels, etc. The two lungs are roughly cone - shaped , tapering at the top and broad at the bottom. The left lung is slightly smaller to accomodate the heart  in between .

PARTS OF RESPIRATORY SYSTEM ...... 

BREATHING- RESPIRATORY CYCLE 

The respiratory cycle consists of inspiration , expiration, and a very short respiratory pause. 

In normal adults, the breathing rate is 12-18 breaths/min. 

1. INSPIRATION - It results in the increase of the chest cavity which increases the action of the ribs and diaphragm. 

The ribs are moved upward and outward, enlarging the chest cavity. 

Diaphragm is a muscular tissue, which normally remains arched upward like a dome, towards the base of lungs. 

On contraction, it falls or flattens from dome- shaped outline of an almost horizontal plane and thus contributes, to the enlargement of the chest cavity. 

As the diaphragm flattens, it presses the organ inside the and with the abdominal mucles relaxed , the abdominal wall moves outwards. 

2. EXPIRATION -    It is a result of reverse movements of the ribs and diaphragm. 

The external muscles relax and the ribs automatically get depressed . The diaphragm is relaxed and is moved upwards to its dome like outline . The cavity of the thorax is diminished and the lungs are compressed, forcing the air out into the atmosphere . 

RESPIRATORY SYSTEM DISORDERS -   

1. ASTHMA- Asthma is an inflammatory disease of the air ways associated with episodes of reversible over-reactivity of the airway smooth muscle 

The mucous membrane and muscle layers of the bronchi become thickened and the mucous glands enlarge reducing airflow in the lower respiratory tract. 

2. SILICOSIS- This may be caused by longterm exposure to dust containing silicon compounds.

High risk industries are quarrying, granite, slate, sandstone, mining, stone masonry, sand blasting, and glass and pottery work.

Silicosis appears to redispose to the development of tuberculosis, which rapidly progresses to tubercular bronchopnuemonia and possibly military TB. 

Gradual destruction of lung tissue leads in progressive reduction in pulmonary function, pulmonary hypertension and heart failure.

3.ASBESTOSIS - Asbestosis, caused by inhaling asbestos fibres, usually develops after 10 to 20 years exposure, but sometimes after only 2 years. Asbestos miners and workers involved in making and using products containing asbestos are at risk. 

4. EMPHYSEMA - Emphysems is a long term, progressive disease of the lungs primarily causes shortness of breath due to over-inflation of the alveoli or air sacs of lungs. 

5. CHRONIC OBSTRUCTIVE PULMONARY DISEASE - It is an obstructive lung disease because air flow is reduced or stopped. When the air sacs are damaged,, the airways collapse.

This makes it difficult for the lungs to empty the air and th air is trapped in the alveoli. 

5. Lung Cancer - Lung cancer is the uncontrolled growth of abnormal cells that start off in one or both lungs; usually in the cells that line the air passages. The abnormal cells do not develop into healthy lung tissue, they divide rapidly and form tumors.

Effects of smoking on your body ..................