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Human Anatomy
OVERVIEW OF THE BASIC ACTIVITIES OF LIFE
A living organism is in homeostasis if all of its organ systems work together as a
single unit to regulate the basic activities of life. They include:
1) Respiration
We need energy to grow, to
maintain homeostasis, to
defend ourselves from foreign
molecules, to repair cells and to
reproduce. The cells undergo
cellular respiration, aeorobic
respiration (oxygen is needed).
Respiration refers to the intake
of oxygen in the lungs and the
oxidation of molecules such as
carbohydrates, lipids and
proteins to make energy.
Source(figure):http://ejels.blackgold.ca/projects/Grade_8/Tael
ar/Body_Systems_Website/respiratory-system.jpg
External respiration is the
ventilation of air into the lungs,
and the gas exchange between
the alveoli and the blood
capillaries. Blood exchanges
carbon dioxide for oxygen from
the lungs. Carbon dioxide is
exhaled out.
Internal respiration is the gas exchange between the blood and the tissues.
Tissues exchange the carbon dioxide for the oxygen. The de-oxygenated blood
(blood with carbon dioxide) will go back to the lungs to get oxygenated, and the
cycle will repeat again.
2) Nutrient Transport
The cardiovascular system consists of the heart,
blood vessels and blood. Deoxygenated blood
comes to the right side of heart to be pumped up
into the lungs to get oxygenated. Then the
oxygenated blood goes to the left side of the heart
to be pumped out from the aorta to the tissues
where they exchange wastes and carbon dioxide
Source(figure):http://www.urgomedical.com/var/ezflow_site/st
orage/images/media/images/venous-system-02/2059-1-engGB/venous-system-02.jpg
with oxygen and nutrients by diffusion. The capillaries containing deoxygenated
blood go back to the heart and the cycle repeats.
3) Digestion
Humans are heterotrophs as they do not have mechanisms to make their own
nutrients. Without nutrients, our system would shut down because it would lack
the energy for growth, repair and overall functioning.
We ingest food to obtain energy and nutrition. Digestion of food is the breakdown
of molecules into smaller ones
that can be absorbed into the
blood, which will transport them
to the cells as needed.
Macromolecules include
carbohydrates, proteins, lipids
and nucleic acids. Carbohydrates
have monosaccharides as their
smallest unit, proteins have
amino acids, lipids have glycerol
and fatty acids, whereas nucleic
acids have nucleotides.
The digestive tract of humans
starts with the oral cavity, then
pharynx, followed by esophagus,
the stomach, the small intestine,
the large intestine and the anus.
The breakdown of carbohydrates
starts in the oral cavity. The food
moves down the esophagus
(peristalsis) by involuntary
contractions. The stomach
Source(figure):http://upload.wikimedia.org/wikipedia/common
secretes acidic juice and
s/thumb/c/c5/Digestive_system_diagram_edit.svg/340pxproteinases (enzymes that break
Digestive_system_diagram_edit.svg.png
down proteins) to kill bacteria and
break down proteins into amino
acids. The liver and the pancreas assist the small intestine by secreting bile and
pancreatic juice to break down lipids, more proteins and carbohydrates. Amino
acids, monosaccharides and fatty acids are then allowed to be absorbed into the
bloodstream. The longer the small intestine, the greater the digestion and
absorption. The large intestines allow for the absorption of any water or salts left
over. Rectum stores feces before elimination through the anus.
5) Excretion
Excretion refers to the removal of metabolic wastes produced in the body. The
main organs of excretion are skin, lungs, liver and most importantly kidneys.
Sweat glands in the skin excrete water (with dissolved salts).
We exhale carbon dioxide from the lungs where the gas exchange happened
between alveoli and capillaries.
The liver is responsible for the breakdown
of amino acids, a process that releases
ammonia, which is converted into urea to
decrease its toxicity. Urea diffuses into
the blood and is finally secreted from the
kidneys.
Kidneys are responsible for filtering the
blood, processing the filtrate into urine
and releasing urine into the ureters. The
bladder stores the urine before excretion
through the urethra.
*** NOTE: Elimination (following
digestion) rids us of undigested material.
Excretion is the removal of metabolic
products.
6) Movement
The musculoskeletal system provides the framework for the human body.
Muscles are attached to the bones to allow locomotion.
Our skeletal system provides physical support, organ protection, and movement.
Our skeleton is made out of cartilage (flexible connective tissue) and bone
(enduring connective tissue).
Our muscular system generates force. There are three types of muscle: skeletal
(used for voluntary movements), smooth (surrounds the organs, mostly), and
cardiac (makes up the muscle tissue of the heart).
7) Nervous System
The nervous system allows us to receive and respond to a stimulus from the
external and internal environment. The functional unit of the nervous system is
the neuron, which is responsible for nerve conduction. Neuroglia makes up the
team of cells that provides nutrition and support for the neurons.
The nervous system has two divisions: the peripheral and the central nervous
system.
The central nervous system consists of the brain and the spinal cord. The
peripheral nervous system consists of the efferent neurons (to the brain) and
afferent neurons (away from the brain).
8) Endocrine System
It is used to coordinate the activities of organ systems, internally. Endocrine
glands make and secrete hormones directly into the bloodstream as needed.
Some of them are:
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pituitary gland which releases ADH to increase the water absorption in the
blood from the nephron
thyroid gland produces calcitonin hormone to decrease blood calcium
level
parathyroid gland produces PTH to increase blood calcium levels by
stimulating calcium absorption from the digestive tract
adrenal cortex produces aldosterone to promote sodium and water
absorption into the blood
pancreas produces glycagon to increase blood glucose level, and insulin
to lower blood glucose level
heart produces ANP to prevent the release of aldosterone from the
adrenal cortex thus allowing the excretion of sodium and water with urine.
kidneys make renin – enzyme that eventually leads to the stimulation of
adrenal cortex to produce aldosterone. They also make erythropotein –
glycoprotein that promotes red blood cell production
***NOTE: Endocrine system responds slower than the nervous system.