I choose to start with the overview of the
human body so we can be familiar with the terms I'll be using as we proceed
.
This article covers just the external human
body only.
The human body is the entire structure of a
human organism, and consists of a head, neck, torso, two arms and two legs.
Constituents
of the human body
In a normal man weighing 60 kg
Constituent Weight Percent
of atoms
Hydrogen 6.0 kg 63%
Oxygen 38.8 kg 25.5%
Carbon 10.9 kg 9.5%
Nitrogen 1.9 kg 1.4%
Calcium 1.2 kg 0.2%
Phosphorus 0.6 kg 0.2%
Potassium. 0.2 kg 0.07%
Body proportion
The average height of an adult male human
(in developed countries) is about 1.7–1.8 m (5'7" to 5'11") tall
and the adult female is about 1.6–1.7 m (5'2" to 5'7") tall.
Height is largely determined by genes and diet. Body type and composition are
influenced by factors such as genetics, diet, and exercise.
Organ systems
The organ systems of the body include the
musculoskeletal system, cardiovascular system, digestive system, endocrine
system, integumentary system, urinary system, lymphatic system, immune system,
respiratory system, nervous system and reproductive system.
Cardiovascular
system
Cardiovascular system and Human heart
The cardiovascular system comprises the
heart, veins, arteries and capillaries. The primary function of the heart is to
circulate the blood, and through the blood, oxygen and vital minerals are
transferred to the tissues and organs that comprise the body. The left side of
the main organ (left ventricle and left atrium) is responsible for pumping
blood to all parts of the body, while the right side (right ventricle and right
atrium) pumps only to the lungs for re-oxygenation of the blood. The heart
itself is divided into three layers called the endocardium, myocardium and
epicardium,(liquidation) which vary in thickness and function.
Digestive system
Digestive system and Human gastrointestinal
tract
The digestive system provides the body's
means of processing food and transforming nutrients into energy. The digestive
system consists of the buccal cavity, esophagus, stomach, small intestine,
large intestine ending in the rectum and anus. These parts together are called
the alimentary canal (digestive tract).
Integumentary system
The integumentary system is the largest
organ system in the human body, and is responsible for protecting the body from
most physical and environmental factors. The largest organ in the body is the
skin. The integument also includes appendages, primarily the sweat and
sebaceous glands, hair, nails and arrectores pillorum (tiny muscles at the root
of each hair that cause goose bumps).
Lymphatic system
Lymphatic system and Immune system
The main function of the lymphatic system
is to extract, transport and metabolise lymph, the fluid found in between
cells. The lymphatic system is very similar to the circulatory system in terms
of both its structure and its most basic function (to carry a body fluid).
Musculoskeletal system
The human musculoskeletal system consists
of the human skeleton, made by bones attached to other bones with joints, and
skeletal muscle attached to the skeleton by tendons.
Bones
Human skeleton and List of bones of the human
skeleton
An adult human has approximately 206
distinct bones:
Spine and vertebral column (26)
Cranium (8)
Face (14)
Hyoid bone, sternum and ribs (26)
Upper extremities (70)
Lower extremities (62)
Nervous system
Nervous system and Human brain
The nervous system consists of cells that
communicate information about an organism's surroundings and itself. The
nervous system of humans is divided into the central nervous system (CNS) and
peripheral nervous system (PNS).
Reproductive system
Human reproduction takes place as internal
fertilization by sexual intercourse. During this process, the erect penis of
the male is inserted into the female's vagina until the male ejaculates semen,
which contains sperm, into the female's vagina. The sperm then travels through
the vagina and cervix into the uterus or fallopian tubes for fertilization of
the ovum.
The human male reproductive system is a
series of organs located outside the body and around the pelvic region of a
male that contribute towards the reproductive process. The primary direct
function of the male reproductive system is to provide the male gamete or
spermatozoa for fertilization of the ovum.
The major reproductive organs of the male
can be grouped into three categories. The first category is sperm production
and storage. Production takes place in the testes which are housed in the
temperature regulating scrotum, immature sperm then travel to the epididymis
for development and storage. The second category are the ejaculatory fluid
producing glands which include the seminal vesicles, prostate, and the vas
deferens. The final category are those used for copulation, and deposition of
the spermatozoa (sperm) within the female, these include the penis, urethra,
vas deferens and Cowper's gland.
The human female reproductive system is a
series of organs primarily located inside of the body and around the pelvic
region of a female that contribute towards the reproductive process. The human
female reproductive system contains three main parts: the vagina, which acts as
the receptacle for the male's sperm, the uterus, which holds the developing
fetus, and the ovaries, which produce the female's ova. The breasts are also an
important reproductive organ during the parenting stage of reproduction.
The vagina meets the outside at the vulva,
which also includes the labia, clitoris and urethra; during intercourse this
area is lubricated by mucus secreted by the Bartholin's glands. The vagina is
attached to the uterus through the cervix, while the uterus is attached to the
ovaries via the fallopian tubes. At certain intervals, typically approximately
every 28 days, the ovaries release an ovum, which passes through the fallopian
tube into the uterus. The lining of the uterus, called the endometrium, and
unfertilized ova are shed each cycle through a process known as menstruation.
(Culled
from wikipedia)
