Human body in short(for medical entrance)

Here I am about to give a short description of human body and it’s internal system in short, which might be a helpful guide for school students and students preparing for medical entrance examinations.

Head

This is the most important part of the body, which controls the whole of human body by the usage of central nervous system.

The head contains the brain, which lies inside the cranium. The head and the spinal cord constitutes the central nervous system.

There are 12 pairs of cranial nerve

1.Olfactory 

           

2.Optic

3.Oculomotor

4.Trochlear

5.Trigeminal

6.Abducens

7.Facial

8.Auditory/ vestibulo cochlear

9.Glossopharengeal

10.Vagus(largest cranial nerve)

11.Spinal accessory

12.Hypoglossal

Among these nerves, vagus nerve is the largest and the only nerve which extends up to the abdominal part.

The functions are as follows in brief

1. Olfactory – for olfaction or smell

2. Optic--- vision

3. Oculomotor--- movement of eyeball/pupilliary constriction and accommodation

4. Trochlear--- movement of eyeball

5. Trigeminal--- opening and closing of mouth

6. Abducens--- movement of eyeball

7. Facial--- taste and facial movement

8. Auditory/ vestibulo cochlear--- hearing and balancing

9. Glossopharengeal--- chemo/baroreception, taste, swallowing, salivation

10. Vagus--- visceral sensation and swallowing

11. Spinal accessory—movement of head and abducens

12. Hypoglossal--- movement of tongue

Respiratory system

The different parts of the respiratory system are as follows

Nasal cavity->pharynx-->larynx-> trachea-> bronchus-> bronchiole--> alveolar sac->alveolus

Trachea is the largest part of the respiratory tract and consists of tracheal rings. These tracheal rings are made up of hyaline cartilage.

Lungs is the largest organ of the lower respiratory tract.

Lungs consists of the larynx, trachea, bronchus, bronchioles, alveolar sac, alveolus.

The lungs remains within the pleural cavity of the thorax.

The alveoli are the tiny air sacs where gaseous exchange takes place.

Digestive system

The  digestive system starts from the oral cavity.

Inside the oral cavity there remains 

1> palate

2> tongue

3> 32 pairs of teeth( incisors, canine, premolar, molar)

Dental formula

Adult =2123/2123

Deciduous=212/212

The general dental formula is ICPM \ICPM

I= Incisor    C=Canine     P=Premolar       M=Molar

This means that in human beings the upper palate has two incisors, one canine, two premolars and three molars.

This is also same with the lower palate.

Now comes the salivary glands. There are a number of salivary glands present in the mouth.

Some important of them are

1> parotid

2> sub mandibular

3>sub lingual

Digestive tract

1> pharynx

2> oesophagus

3> stomach

4> duodenum      

5> jejunum                              6> ileum

7> colon               

8> rectum

9> anus

There are also some other parts which are present in  the digestive tract

They are cecum and appendix.

In human beings , the appendix is a vestigial organ.

Now the list of digestive juices are being given

Digestive juice

1> salivary glands release salivary amylase, which is a fluid that begins the process of breaking down the food as it is chewed. Salivary amylase specifically targets the starch in food.

2> Once food reaches the stomach, the epithelial cells produce what are commonly called gastric juices. Gastric juices include a combination of

·         hydrochloric acid,

·          pepsinogen

·          mucus.

 The hydrochloric acid activates pepsin, which controls the process that converts proteins into peptides.
The combination of acids and churned foods within the stomach is known as chyme.

 3>Bile from the liver aid in digestion of fats, while the pancreatic juices trypsin, lipases and amylase break down the proteins, the fats in starches and the fat that is emulsified by the liver bile.

4> The intestinal enzymes include

·         peptidases,

·         sucrase,

·         lactase

·         maltase

are responsible for the digestion of peptides( by peptidases), maltose(by maltase), sucrose(by sucrase) and lactose(by lactase). 

 

5> pancreatic juice includes

·         Trypsinogen

·         Chymotrypsinogen

·         Elastase

·         Carboxypeptidase

·         Pancreatic lipases

·         Nucleases

·         Amylase

Endocrine system

Glands and hormone production

glands	Function
Adrenal	These are attached to the kidney surfaces.  Their hormones control  growth, sugar metabolism, kidney function and stress.
Hypothalamus	Found at the base of the brain. It is the main controlling gland of all other hormonal glands.
Ovaries	Produce the female hormones oesterogen and progesterone.
Pancreas	Located in the fold of the duodenum. Produces insulin in order to control sugar metabolism.
Parathyroids	Located near the thyroid glands near the neck.Control calcium and phosphorous deposition.
Pituitary	Found at the base of the brain. Hormones control growth, reproduction, lactation and stress.
Placenta	Membranes that cover the foetus. Maintains pregnancy and produces female hormones.
Testicles	Produce the male hormone testosterone.
Thyroid	Controls metabolism and growth.

Hormone groups

Endocrine gland	Hormone produced	Main function of hormone
Hypothalamus	Thyrotropin releasing hormone Dopamine Growth hormone releasing hormone Somatostatin Gonadotropin releasing hormone Corticotrophin releasing hormone Vasopressin	Stimulate thyroid stimulating hormone release from anterior pituitary Inhibit prolactin Stimulate growth hormone release from anterior pituitary Inhibit growth hormone release from anterior pituitary Stimulate follicle stimulating hormone from anterior pituitary Stimulate adrenocorticotropic  hormone release from anterior pituitary Increases water permeability  in the distal convoluted tubule and collecting duct of nephrons, thus promoting water reabsorption and increasing blood volume.
Posterior pituitary	Antidiuretic hormone(ADH) Oxytocin	Increases water permeability  in the distal convoluted tubule and collecting duct of nephrons, thus promoting water reabsorption and increasing blood volume. In females uterine contraction during birth, lactation when nursing
Anterior pituitary	TSH(thyroid stimulating hormone) ACTH(adenocorticotrophic hormone) FSH(follicle stimulating hormone) LH(luteinizing hormone) PRL(prolactin) GH(growth hormone) MSH(melanocyte stimulating hormone)	Stimulates T3, T4 production Stimulates corticosteroid and androgen synthesis Maturation of ovarian follicles in ovary and seminiferous tubules in testes Stimulates ovulation and formation of corpus luteum in females and stimulates testosterone synthesis from leydig cells in males. Stimulates milk synthesis and release from mammary glands Stimulates growth and cell reproduction Stimulates melanin synthesis and release from skin/hair melanocytes
Thyroid	Triiodothyronine Thyroxine Calcitonin	Stimulates body oxygen and energy consumption, thereby increasing the basal metabolic rate Stimulates body oxygen and energy consumption, thereby increasing the basal metabolic rate Stimulates osteoblasts and thereby bone construction
Parathyroid	PTH(parathyroid hormone)	Stimulates calcium release from bones and thereby increasing blood calcium level
Adrenal cortex	Aldosterone Glucocorticoids Sex steroids	Stimulates sodium reabsorption in kidneys Stimulates passive water reabsorption in kidneys thus increasing blood volume and blood pressure Stimulates gluconeogenesis Not that much effect in males but brings masculinizing effects in females
Adrenal medulla	Adrenalin Noradrenalin	Fight or flight response, increases blood pressure
Pancreas	Insulin(from beta cells of islet cells) Glucagon(from alpha cells of islet cells) Stomatostatin(from delta cells of islet cells)	Decreases blood sugar level and increases glycogen level in liver Increases blood glucose level Inhibit release of insulin and glucagon
Kidney	Renin(from juxtaglomerular cells)	Activates rennin angiotensin system by producing angiotensin1 of angiotensinogen
Testes	Androgens(chiefly testosterone from leydig cells)	Growth of muscle mass and strength, increased bone density, growth and strength
Ovarian follicle and corpus luteum	Progesterone Estrogen Inhibin	Support pregnancy Promote formation of female secondary characteristics Inhibit production of FSH from anterior pituitary
Uterus(when pregnant)	Prolactin Relaxin	Milk production in mammary glands Relaxes the muscles of vagina during parturition