Embedded Files
The human body is a single structure but it is made up of billions of smaller structures of four major kinds: cells, tissues, organs, and systems. An organ is an organization of several different kinds of tissues so arranged that together they can perform a special function.
The Major Organs In The Human Body
HEART
The heart is the major organ of the cardiovascular system. It is the size of a fist. It is located between your lungs in the middle of your chest, slightly tilted to the left. It pumps blood through a network of arteries and veins throughout the body.
BRAIN
The brain is one of the most complex organs of the body, made up of more than 100 billion nerves that help other organs communicate with each other.
LUNGS
The lungs are a pair of spongy, air-filled organs that are part of the respiratory system and located on either side of the chest.
KIDNEYS
The kidneys are a pair of bean-shaped organs that are part of the urinary system and located on either side of the spine, below the ribs, and deep in the abdomen.
LIVER
The liver is the largest internal solid organ in the body located on the right side of the abdomen. It has multiple functions, the most important being energy production and metabolism.
SKIN
The skin acts as a protective barrier against bacteria or fungi from entering the body. It maintains body temperature and pH balance.
BONES
Bones support organs and muscles but also play a major role in calcium metabolism in the body.
ADRENAL GLANDS
These glands secrete hormones that help the body deal with stress. If these organs fail, the body may go into a potentially fatal shock.
HEMATOPOIETIC SYSTEM
Blood consists of red and white cells and platelets. If this organ system fails, it can lead to severe bleeding or death from severe infections.
The Systems In Human Body
A system is an organization of varying numbers and kinds of organs so arranged that together they can perform complex functions for the body. Some of these systems include: -
The cardiovascular system
The Digestive system
The Respiratory system
The Urinary system
The Nervous system
The Skeletal system.
1) Human Cardiovascular System
The human cardiovascular system organ conveys blood through vessels to and from all parts of the body, carrying nutrients and oxygen to tissues and removing carbon dioxide and other wastes.
It is a closed tubular system in which the blood is propelled by the heart. Two circuits, the pulmonary and the systemic, consist of arterial, capillary, and venous components.
The primary function of the heart is to serve as a muscular pump propelling blood into and through vessels to and from all parts of the body.
The arteries, which receive this blood at high pressure and velocity and conduct it throughout the body, have thick walls that are composed of elastic fibrous tissue and muscle cells.
The arterial tree—the branching system of arteries—terminates in short, narrow, muscular vessels called arterioles, from which blood enters capillaries.
These thin, microscopic capillaries are permeable to vital cellular nutrients and waste products that they receive and distribute.
From the capillaries, the blood, now depleted of oxygen and burdened with waste products, moving more slowly and under low pressure, enters small vessels called venules that converge to form veins, ultimately guiding the blood on its way back to the heart.
Blood Circulation System
The Heart
2) Human Digestive System
The human digestive system is the system used in the human body for the process of digestion.
The human digestive system consists primarily of the digestive tract or the series of structures and organs through which food and liquids pass during their processing into forms absorbable into the bloodstream.
The system also consists of the structures through which wastes pass in the process of elimination and other organs that contribute juices necessary for the digestive process.
The digestive tract begins at the lips and ends at the anus. It consists of: -
1) The oral cavity, with its teeth, for grinding the food, and its tongue, which serves to knead food and mix it with saliva;
2) The throat or pharynx;
3) The esophagus;
4) The stomach;
5) The small intestine, consists of villi, which are finger-like projections that increase the surface area of the small intestine.
6) The large intestine
7) The rectum.
Glands contributing digestive juices include the salivary glands, the gastric glands in the stomach lining, the pancreas, and the liver and its adjuncts—the gallbladder and bile ducts.
All of these organs and glands contribute to the physical and chemical breaking down of ingested food and to the eventual elimination of nondigestible wastes.
The Digestive System
3) Human Respiratory System
The human respiratory system is the system in humans that takes up oxygen and expels carbon dioxide.
The lungs are located in the thorax, where its delicate tissues are protected by the bony and muscular thoracic cage.
The lung provides the tissues of the human body with a continuous flow of oxygen and clears the blood of the gaseous waste product, carbon dioxide.
Atmospheric air is pumped in and out regularly through a system of pipes, called conducting airways, which join the gas-exchange region with the outside of the body.
The airways can be divided into upper and lower airway systems. The transition between the two systems is located where the pathways of the respiratory and digestive systems cross, just at the top of the larynx.
The upper airway system comprises of:-
The nose and the paranasal cavities (or sinuses),
The pharynx (or throat), and partly also the oral cavity, since it may be used for breathing.
The lower airway system consists of: -
The larynx,
The trachea,
The stem bronchi,
The intrapulmonary bronchi,
The bronchioles,
Alveolar ducts.
For respiration, the collaboration of other organ systems is essential.
The diaphragm, as the main respiratory muscle, and the intercostal muscles of the chest wall play an essential role by generating, under the control of the central nervous system, the pumping action on the lung.
The muscles expand and contract the internal space of the thorax, the bony framework of which is formed by the ribs and the thoracic vertebrae.
The lung and chest wall (ribs and muscles) also contribute to respiration.
The blood, as a carrier for the gases, and the circulatory system are mandatory elements of a working respiratory system
The Human Respiratory System
4) Human Urinary System
The Human Urinary System is the organ system that includes: -
The Kidneys, where urine is produced,
The ureters
Bladder
Urethra for the passage, storage, and voiding of urine.
In many respects, the human excretory, or urinary system, resembles those of other mammalian species, but it has its own unique structural and functional characteristics.
The terms excretory and urinary emphasize the elimination function of the system.
The kidneys, however, both secrete and actively retain within the body certain substances that are as critical to survival as those that are eliminated.
The system contains two kidneys, which control the electrolyte composition of the blood and eliminate dissolved waste products and excess amounts of other substances from the blood.
The substances are excreted in the urine, which passes from the kidneys to the bladder by way of two thin muscular tubes called the ureters.
The bladder is a sac that holds the urine until it is eliminated through the urethra.
The Human Urinary System
5) Human Nervous System
The human nervous system is an organized group of cells specialized for the conduction of electrochemical stimuli from sensory receptors through a network to the site at which a response occurs.
All living organisms can detect changes within themselves and in their environments.
Changes in the external environment include those of light, temperature, sound, motion, and odour.
Changes in the internal environment include those in the position of the head and limbs as well as in the internal organs.
Once detected, these internal and external changes must be analyzed and acted upon to survive.
As life on Earth evolved and the environment became more complex, the survival of organisms depended upon how well they could respond to changes in their surroundings. One factor necessary for survival was a speedy reaction or response.
Since communication from one cell to another by chemical means was too slow to be adequate for survival, a system evolved that allowed for faster reactions.
That system was the nervous system, which is based upon the almost instantaneous transmission of electrical impulses from one region of the body to another along specialized nerve cells called neurons.
Nervous systems are of two general types: -
Diffuse
Centralized
In the diffuse type of system, found in lower invertebrates, there is no brain, and neurons are distributed throughout the organism in a netlike pattern.
In the centralized systems of higher invertebrates and vertebrates, a portion of the nervous system has a dominant role in coordinating information and directing responses.
This centralization reaches its culmination in vertebrates, which have a well-developed brain and spinal cord. Impulses are carried to and from the brain and spinal cord by nerve fibres that make up the peripheral nervous system.
The Human Nervous System
Nerves
6) Human Skeletal System
The human skeletal system is the internal skeleton that serves as a framework for the body.
This framework consists of many individual bones and cartilages. There also are bands of fibrous connective tissue—the ligaments and the tendons—in an intimate relationship with the parts of the skeleton.
The human skeleton consists of two principal subdivisions, each with origins distinct from the others and each presenting certain individual features. These are: -
(1) the axial, comprising the vertebral column—the spine—and much of the skull,
(2) the appendicular, to which the pelvic (hip) and pectoral (shoulder) girdles and the bones and cartilages of the limbs belong.
The axial skeleton is a third subdivision, the visceral, comprising the lower jaw, some elements of the upper jaw, and the branchial arches, including the hyoid bone.
When one considers the relation of these subdivisions of the skeleton to the soft parts of the human body it is clear that the functions of the skeleton are of three different types:
Support,
Protection, and
Motion.
1) Support
Support is the most primitive and the oldest; likewise, the axial part of the skeleton was the first to evolve.
The vertebral column, corresponding to the notochord in lower organisms, is the main support of the trunk.
2) Protection
The central nervous system lies largely within the axial skeleton, the brain is well protected by the cranium and the spinal cord by the vertebral column, through the bony neural arches and the intervening ligaments.
Protection of the heart, lungs and other organs and structures in the chest creates a problem somewhat different from that of the central nervous system.
These organs, the function of which involves motion, expansion, and contraction, must have a flexible and elastic protective covering.
Such a covering is provided by the bony thoracic basket, or rib cage, which forms the skeleton of the wall of the chest, or thorax.
The connection of the ribs to the breastbone—the sternum—is in all cases a secondary one, brought about by the relatively pliable rib (costal) cartilages.
The small joints between the ribs and the vertebrae permit a gliding motion of the ribs on the vertebrae during breathing and other activities.
The motion is limited by the ligamentous attachments between ribs and vertebrae.
3) Motion
The third general function of the skeleton is that of motion.
The great majority of the skeletal muscles are firmly anchored to the skeleton, usually to at least two bones and in some cases to many bones.
Thus, the motions of the body and its parts, all the way from the lunge of the football player to the delicate manipulations, are made possible by separate and individual engineering arrangements between muscle and bone.
The Human Skeletal System
The 5 Senses
The five sensory 'gatekeepers' of our bodies – taste, smell, touch, sight and hearing – help us survive.
Every day, our ears, nose, tongue, eyes and skin are constantly bombarded with massive amounts of information from the environment around us that must be processed and responded to.
(i) The Eyes
(i) The Eyes
Translate Light into Image Signals for the Brain to Process
Translate Light into Image Signals for the Brain to Process
The eyes sit in the orbit of the skull, protected by bone and fat.
The white part of the eye is the sclera. It protects interior structures and surrounds a circular portal formed by the cornea, iris, and pupil.
The cornea is transparent to allow light to enter the eye and curved to direct it through the pupil behind it.
The pupil is an opening in the coloured disk of the iris.
The iris dilates or constricts, adjusting how much light passes through the pupil and onto the lens.
The curved lens then focuses the image onto the eye’s interior layer, the retina.
The retina is a delicate membrane of nervous tissue containing photoreceptor cells.
These cells, the rods and cones, translate light into nerve signals. The optic nerve carries the signals from the eye to the brain, where it gets interpreted and forms visual images.
The Eye
(ii) The Ear
(ii) The Ear
Uses Bones and Fluid to Transform Sound Waves into Sound Signals
Uses Bones and Fluid to Transform Sound Waves into Sound Signals
Music, laughter, car honks — all reach the ears as sound waves in the air.
The outer ear funnels the waves down the ear canal (the external acoustic meatus) to the tympanic membrane (the “ear drum”).
The sound waves beat against the tympanic membrane, creating mechanical vibrations in the membrane.
The tympanic membrane transfers these vibrations to three small bones, known as auditory ossicles, found in the air-filled cavity of the middle ear.
These bones – the malleus, incus, and stapes – carry the vibrations and knock against the opening to the inner ear.
The inner ear consists of fluid-filled canals, including the spiral-shaped cochlea.
As the ossicles pound away, specialized hair cells in the cochlea detect pressure waves in the fluid.
They activate nervous receptors, sending signals through the cochlear nerve toward the brain, which interprets the signals as sounds.
The Ear
(iii) The Skin
(iii) The Skin
Specialized Receptors in the Skin Send Touch Signals to the Brain
Specialized Receptors in the Skin Send Touch Signals to the Brain
The Skin consists of three major tissue layers: -
The Outer Epidermis,
Middle dermis, and
Inner hypodermis.
Specialized receptor cells within these layers detect tactile sensations and relay signals through peripheral nerves toward the brain.
The presence and location of the different types of receptors make certain body parts more sensitive.
Merkel cells, for example, are found in the lower epidermis of lips, hands, and external genitalia.
Meissner corpuscles are found in the upper dermis of hairless skin — fingertips, nipples, the soles of the feet, etc.
Both of these receptors detect touch, pressure, and vibration.
Other touch receptors include Pacinian corpuscles, which also register pressure and vibration, and the free endings of specialized nerves that feel pain, itch, and tickle.
The Skin
(iv) The Nose
Chemicals in the Air Stimulate Signals the that Brain Interprets as Smells
Chemicals in the Air Stimulate Signals the that Brain Interprets as Smells
The sense of smell is called olfaction.
It starts with specialized nerve receptors located on hairlike cilia in the epithelium at the top of the nasal cavity.
When we sniff or inhale through the nose, some chemicals in the air bind to these receptors. That triggers a signal that travels up a nerve fiber, through the epithelium and the skull bone above, to the olfactory bulbs.
The olfactory bulbs contain neuron cell bodies that transmit information along the cranial nerves, which are extensions of the olfactory bulbs.
They send the signal down the olfactory nerves, toward the olfactory area of the cerebral cortex.
The Nose
(v) The Tongue
The Tongue Is the Principal Organ of Taste
The Tongue Is the Principal Organ of Taste
The small bumps on the top of the tongue are called papillae.
Many of them, including circumvallate papillae and fungiform papillae, contain taste buds.
When we eat, chemicals from food enter the papillae and reach the taste buds.
These chemicals (or tastants) stimulate specialized gustatory cells inside the taste buds, activating nervous receptors.
The receptors send signals to fibers of the facial, glossopharyngeal, and vagus nerves.
Those nerves carry the signals to the medulla oblongata, which relays them to the thalamus and cerebral cortex of the brain.
The Tongue
Page updated
Google Sites
Report abuse