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
|
|
|
|