Organs of the Body & Organs Systems of the Body
The pharynx, or throat, is a funnel-shaped tube connected to the posterior end of the mouth. Saliva moistens dry food and contains salivary amylase, a digestive enzyme that begins the digestion of carbohydrates. After puberty, the vagina is colonized by Lactobacillus aerophilus that ferment glycogen to maintain an acid pH. Retrieved 1 June All other sections of the human body are drained by the thoracic duct. These are white blood cells that are very important for fighting infection.
What is the Immune System to Your Health?
The human body is the most complicated machine in the world and the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs The human body is the most complicated machine in the world. We see with it, hear with it, breathe with it, walk and run with it, and sense pleasure with it.
Its bones, muscles, arteries, veins and internal organs are organized with marvellous design, and when we examine this design in detail we find even more amazing facts. The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs. By the time the human reaches adulthood, the body consists of close to 10 trillion cells, the basic unit of life.
Groups of cells combine and work in tandem to form tissue, which combines to form organs, which work together to form 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. The human skeleton consists of both fused and individual bones supported and supplemented by ligaments, tendons, muscles and cartilage.
It serves as a scaffold which supports organs, anchors muscles, and protects organs such as the brain, lungs and heart. The blood flows from the heart into arteries, then to capillaries, and returns to the heart through veins. The plasma is mostly water All blood cells are manufactured by stem cells, which live mainly in the bone marrow, via a process called hematopoiesis. The stem cells produce hemocytoblasts that differentiate into the precursors for all the different types of blood cells.
Hemocytoblasts mature into three types of blood cells: The leukocytes are further subdivided into granulocytes containing large granules in the cytoplasm and agranulocytes without granules.
The agranulocytes are lymphocytes consisting of B cells and T cells and monocytes. Lymphocytes circulate in the blood and lymph systems, and make their home in the lymphoid organs. All of the major cells in the blood system are illustrated below. There are —10, WBCs per mm 3 and they live days. About 2,, RBCs are produced each second and each lives for about days They migrate to the spleen to die.
Once there, that organ scavenges usable proteins from their carcasses. A healthy male has about 5 million RBCs per mm 3 , whereas females have a bit fewer than 5 million. Normal Adult Blood Cell Counts. Blood type AB means both antigens are present and type O means both antigens are absent. Type A blood has A antigens and type B blood has B antigens. Some of the blood, but not red blood cells RBCs , is pushed through the capillaries into the interstitial fluid. It flows in the lymphatic vessels and bathes tissues and organs in its protective covering.
There are no RBCs in lymph and it has a lower protein content than blood. The lymph flows from the interstitial fluid through lymphatic vessels up to either the thoracic duct or right lymph duct, which terminate in the subclavian veins, where lymph is mixed into the blood. The right lymph duct drains the right sides of the thorax, neck, and head, whereas the thoracic duct drains the rest of the body. Lymph carries lipids and lipid-soluble vitamins absorbed from the gastrointestinal GI tract.
Since there is no active pump in the lymph system, there is no back-pressure produced. The lymphatic vessels, like veins, have one-way valves that prevent backflow. Additionally, along these vessels there are small bean-shaped lymph nodes that serve as filters of the lymphatic fluid. It is in the lymph nodes where antigen is usually presented to the immune system.
The human lymphoid system has the following: The innate immunity system is what we are born with and it is nonspecific; all antigens are attacked pretty much equally.
It is genetically based and we pass it on to our offspring. Normal flora are the microbes, mostly bacteria, that live in and on the body with, usually, no harmful effects to us.
We have about 10 13 cells in our bodies and 10 14 bacteria, most of which live in the large intestine. There are 10 3 —10 4 microbes per cm 2 on the skin Staphylococcus aureus , Staph. Various bacteria live in the nose and mouth. Lactobacilli live in the stomach and small intestine. The urogenitary tract is lightly colonized by various bacteria and diphtheroids.
After puberty, the vagina is colonized by Lactobacillus aerophilus that ferment glycogen to maintain an acid pH. Normal flora fill almost all of the available ecological niches in the body and produce bacteriocidins, defensins, cationic proteins, and lactoferrin all of which work to destroy other bacteria that compete for their niche in the body. The resident bacteria can become problematic when they invade spaces in which they were not meant to be.
This causes an overgrowth of Clostridium difficile , which results in pseudomembranous colitis, a rather painful condition wherein the inner lining of the intestine cracks and bleeds. A phagocyte is a cell that attracts by chemotaxis , adheres to, engulfs, and ingests foreign bodies. Promonocytes are made in the bone marrow, after which they are released into the blood and called circulating monocytes , which eventually mature into macrophages meaning "big eaters", see below.
Some macrophages are concentrated in the lungs, liver Kupffer cells , lining of the lymph nodes and spleen, brain microglia, kidney mesoangial cells, synovial A cells, and osteoclasts. They are long-lived, depend on mitochondria for energy, and are best at attacking dead cells and pathogens capable of living within cells. Once a macrophage phagocytizes a cell, it places some of its proteins, called epitopes, on its surface—much like a fighter plane displaying its hits.
These surface markers serve as an alarm to other immune cells that then infer the form of the invader. All cells that do this are called antigen presenting cells APCs. The non-fixed or wandering macrophages roam the blood vessels and can even leave them to go to an infection site where they destroy dead tissue and pathogens. Emigration by squeezing through the capillary walls to the tissue is called diapedesis or extravasation. The presence of histamines at the infection site attract the cells to their source.
Natural killer cells move in the blood and lymph to lyse cause to burst cancer cells and virus-infected body cells. They are large granular lymphocytes that attach to the glycoproteins on the surfaces of infected cells and kill them. Polymorphonuclear neutrophils , also called polys for short, are phagocytes that have no mitochondria and get their energy from stored glycogen. They are nondividing, short-lived half-life of 6—8 hours, 1—4 day lifespan , and have a segmented nucleus. The neutrophils provide the major defense against pyogenic pus-forming bacteria and are the first on the scene to fight infection.
They are followed by the wandering macrophages about three to four hours later. The complement system is a major triggered enzyme plasma system. It coats microbes with molecules that make them more susceptible to engulfment by phagocytes. Vascular permeability mediators increase the permeability of the capillaries to allow more plasma and complement fluid to flow to the site of infection.
They also encourage polys to adhere to the walls of capillaries margination from which they can squeeze through in a matter of minutes to arrive at a damaged area. Once phagocytes do their job, they die and their "corpses," pockets of damaged tissue, and fluid form pus. Eosinophils are attracted to cells coated with complement C3B, where they release major basic protein MBP , cationic protein, perforins, and oxygen metabolites, all of which work together to burn holes in cells and helminths worms.
Their lifespan is about 8—12 days. Neutrophils, eosinophils, and macrophages are all phagocytes. Dendritic cells are covered with a maze of membranous processes that look like nerve cell dendrites. Most of them are highly efficient antigen presenting cells. There are four basic types: Langerhans cells, interstitial dendritic cells, interdigitating dendritic cells, and circulating dendritic cells.
Our major concern will be Langerhans cells , which are found in the epidermis and mucous membranes, especially in the anal, vaginal, and oral cavities. These cells make a point of attracting antigen and efficiently presenting it to T helper cells for their activation. Each of the cells in the innate immune system bind to antigen using pattern-recognition receptors. These receptors are encoded in the germ line of each person. This immunity is passed from generation to generation.
Over the course of human development these receptors for pathogen-associated molecular patterns have evolved via natural selection to be specific to certain characteristics of broad classes of infectious organisms. There are several hundred of these receptors and they recognize patterns of bacterial lipopolysaccharide, peptidoglycan, bacterial DNA, dsRNA, and other substances. Clearly, they are set to target both Gram-negative and Gram-positive bacteria.
Lymphocytes come in two major types: B cells and T cells. Their total mass is about the same as that of the brain or liver.