>RESPIRATORY SYSTEM
-It is a biological system consisting of organs and structures that are used in gaseous exchange in human beings.
-This gaseous exchange is primarily concerned with inhalation of oxygen and exhalation of carbon dioxide.
-It also aids in the process of olfaction that is smelling by activating the olfactory receptors during inhalation of oxygen.
-This system includes the following parts:
•Nose:It has external nostrils with tiny hair follicles covering its internal lining for purification of the air entering the body through nostrils.
•Larynx:It is found in front of the neck and consists of two cartilaginous chords which are responsible for vocals as well as aiding respiration. Hence, it is also informally called the voice box.
•Pharynx: It is a wide hollow space where nasal chambers open and a common passage for air and food.The cartilaginous flap called epiglottis ensures the food from entering the Larynx by covering it hence ensuring that air enters Larynx and food goes into the esophagus (food pipe).
•Trachea:Also known as a windpipe it rises below the larynx and moves down to the neck. It's walls comprise C-shaped cartilaginous rings which give hardness to the trachea and maintain it by completely expanding. It extends further down into the breastbone and splits into two bronchi, one for each lung.
•Bronchi: Each bronchi divide into secondary and tertiary bronchioles, and it further branches out into small air-sacs called the alveoli. The alveoli are single-celled sacs of air with thin walls. It facilitates the exchange of oxygen and carbon dioxide molecules into or away from the bloodstream.
•Lungs: They are the primary organs of respiration and are located on either side of the heart, in the thoracic cavity of the chest and their primary function is to facilitate the exchange of gases between the blood and the air. Interestingly, the right lung is quite bigger and heavier than the left lung.
>DIGESTIVE SYSTEM
-It is a system in human beings consisting of gastrointestinal tract and the accessory organs tongue,salivary glands,liver,pancreas, and gall bladder which aids in the process of digestion.
-It involves breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body.
- The process of digestion has three phases:
1.Cephalic Phase:It begins with secretions from gastric glands in response to the sight and smell of food followed by mechanical breakdown of food by chewing, and the chemical breakdown by digestive enzymes, that takes place in the mouth. Saliva contains the digestive enzymes amylase, and lingual lipase, secreted by the salivary and serous glands on the tongue. This produces a bolus which is swallowed down the esophagus to enter the stomach.
2.Gastric Phase:The food is further broken down in stomach by mixing with gastric acid until it passes into the duodenum, the first part of the small intestine.
3.Intestinal Phase:It begins in the duodenum where the partially digested food is mixed with a number of enzymes produced by the pancreas.
-Most of the digestion of food takes place in the small intestine. Water and some minerals are reabsorbed back into the blood in the colon of the large intestine.
-The waste products of digestion (feces) are defecated from the rectum via the anus.
>ENDOCRINE SYSTEM
-It is a messenger system in organisms consisting of feedback loops of hormones which are released by internal glands directly into the circulatory system that targets and regulates distant organs.
-The hypothalamus and pituitary glands are organs of the neuroendocrine system. One of the most important functions of the hypothalamus—it is located in the brain adjacent to the pituitary gland—is to link the endocrine system to the nervous system via the pituitary gland.
-However major endocrine glands are:
•Thyroid Gland - It secrets thyroxine to maintain thyroid levels in the body.
•Pitituary Gland- It secrets growth hormone for the proper growth of the body.
•Pineal Gland- It secrets melatonin which regulates the circadian rhythm (sleep cycle).
•Adrenal Gland- It secrets the adrenaline hormone also known as "Fight or Flight Hormone" which helps human beings to deal with the emotions like stress,fear and excitement.
-Testis in Males: It secretes testosterone required for the production of sperms.
-Ovaries in Females: It secretes estrogen and progesterone for the production of ova(eggs) for fertilization.
-Endocrine glands have no ducts, are vascular, and commonly have intracellular vacuoles or granules that store their hormones.
-Many other organs that are part of other body systems have secondary endocrine functions, including bone, kidneys, liver, heart and gonads. For example, the kidney secretes the endocrine hormone erythropoietin required for the production of erythrocyte (red blood cells).
-Hormones released by endocrine glands can be amino acid complexes, steroids, eicosanoids, leukotrienes, or prostaglandins.
>IMMUNE SYSTEM
-It is a network of biological systems which protects the human beings from various diseases.
-It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as cancer cells, parasitic worms, and also objects such as wood splinters, distinguishing them from the human's own healthy tissue.
-Immunty is if two types:
1.Innate immunity: It provides a preconfigured response to broad groups of situations and stimuli.
2.Adaptive immunity:It provides a tailored response to each stimulus by learning to recognize molecules it has previously enco-untered.
-The mechanism for immunity involves phagocytosis,antimicrobial peptides called defensins and the ability to adapt to recognize pathogens more efficiently.
-It protects the host from infection with layered defenses of increasing specificity.
-Physical barriers prevent pathogens such as bacteria and viruses from entering the organism. If a pathogen breaches these barriers, the innate immune system provides an immediate, but non-specific response.
-If pathogens successfully evade the innate response, then a second layer of protection the adaptive immune system, which is activated by the innate response comes into action.
-Now it adapts to the response during an infection to improve its recognition of the pathogen. This improved response is then retained after the pathogen has been eliminated, in the form of an immunological memory, and allows the adaptive immune system to mount faster and stronger attacks each time this pathogen is encountered.