Science

Introduction to Physiology

Before we can even begin to discuss how the human body works, we first need a model to describe how it exists in time and space.  Thus anatomy is our starting point, the study of structure and the relationships that exist between different structures.  It provides us with a model with which we can study human function, or physiology.  Please login or register to see the full article

Homeostasis

The term that is used to describe this balance of function in the body is homeostasis (homeo = same; stasis = standing still). Each cell in the body has a requirement for nutrition and the elimination of wastes: blood carries nutrition to the cells, and with lymphatic system, carries away cellular wastes and debris for elimination. 

The Skin, Hair and Nails

When we refer to the skin, we are referring to a group of tissues that make up the integumentary system. Of all the body organs, none is more easily assessed in a clinical environment than the skin. The skin is derived from the embryonic ectoderm, as is the nervous system, and thus many skin conditions are partially influenced by the underlying state of the nervous system.

Bones and joints

In Ayurvedic medicine, the bones (asthi dhatu) are considered to be the "support" of the body, and this holds true for physiology as well: without the skeleton humans would be little more than a sack of tissues, muscles and organs writhing about on the floor. Please login or register to see the full article

The Muscular System

There are three primary types of muscle tissue: skeletal, cardiac and smooth. Skeletal muscle attaches to bones, other muscles and even skin, to move the various parts of the skeleton. It is called striated because of the alternating dark and light bands perpendicular to the long axes of muscle fibers that can be seen when examined under a microscope.  Skeletal muscle is for the most part voluntary, which means that that it can be made to contract or relax through conscious control.

The Nervous System

Generally speaking, there are two physiological systems that share in the responsibility of maintaining homeostasis: the endocrine system and the nervous system. Whereas the endocrine system functions to maintain control by releasing substances called hormones that travel through the blood to target specific receptors, the nervous system exerts its influence by the transmission of electrical impulses that travel through nervous tissue. Please login or register to see the full article

Endocrinal Function

There are two principle types of glands in the body: exocrine and endocrine.  Exocrine glands produce substances that are secreted through ducts, into a body cavity, into the lumen of an organ or on a free surface, such as the skin.  You should already be familiar with various exocrine glands, including the sudoriferous glands that produce sweat, mucous glands that produce mucus, and digestive glands that release digestive juices. 

The Cardiovascular System

In order for the different cells in the body to maintain their various activities, they are dependent upon a medium that transports nutrients and wastes, as well as facilitates communication between a group of cells, tissues or organs. This function is performed in large degree by the blood, which is pumped by the heart and carried by the vascular system.

Non-specific Resistance and Immunity

The human body is composed of millions of cells that function together to form the various tissues, organs, and organ systems that make life possible. The activity of these cells, however, depends upon a stable operating environment, called homeostasis. A disruption to this optimal environment, be it an alteration in temperature or a lack of oxygen, is called a stress. 

The Lungs and Breathing

The cells of the body have a constant requirement for oxygen to power the various metabolic reactions that release energy from ingested nutrients to produce ATP. In the process of cellular metabolism carbon dioxide is created as a waste product, which if not eliminated accumulates in the body and dangerously lowers the pH of the tissues and blood, which inhibits a myriad number of vital chemical reactions.  The primary method by which we obtain oxygen and eliminate carbon dioxide is respiration. 

The Digestive System

The digestive system is comprised of a series of organs that participate in the absorption of nutrients and accessory nutrients from our diet that are used to supply the body with energy and the base molecules used to maintain structure of the body. The digestive tract or gastrointestinal tract (GIT) is a tube or canal up to nine meters long that is continuous with the integumentary system, and thus is not only comprised of similar tissues, but maintains similar functions to protect us from the plethora of micro-organisms that are contained within it. Please login or register to see the full article

Liver and Gall Bladder

The liver is the heaviest organ in the body, weighing about 1.4 kg in the average adult, and besides the skin is the largest organ in the body. It is located inferior to the diaphragm, occupying most of the right hypochondriac and part of the epigastric regions of the abdominopelvic cavity. The accessory organ that participates in the digestive function of the liver is the gall bladder, located in a little depression on posterior surface of the liver.Please login or register to see the full article

Metabolism

Metabolism is a term that refers to the sum of all chemical reactions in the body, produced by a delicate balance of catabolic and anabolic activities. Catabolism is the process of breaking complex organic molecules in simpler molecules, releasing the energy contained between chemical bonds and transferring it to ATP, which is then used to fuel a variety of physiological processes. 

The Urinary System

The urinary system is comprised of the two kidneys, the two ureters that lead from each kidney and empty into the urinary bladder, from which extends the urethra that discharges the urine produced in the kidneys. The kidneys are the primary functional unit of the urinary system, the remainder of the organs that comprise the urinary tract functioning simply as storage or to conduct urine outside the body. Please login or register to see the full article

Female Reproduction

The female reproductive organs can be divided into external organs, including the vulva and the breasts, and internal organs such as the uterus and fallopian tubes.

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Male Reproduction

Unlike the female, much of the male reproductive system lies external to the body. Additionally, the mechanism involved in controlling male reproductive physiology is not quite as complex as it is in women. For this reason we can map the various facets of the male reproductive system by following the production and path of sperm cells, beginning with the scrotum.

Fertilization, Pregnancy, and Birth

Unlike mitosis, which occurs throughout the body to replace damaged or otherwise lost cells with genetically identical daughter cells, the cells that are responsible for sexual reproduction develop by meiosis, resulting in genetically different daughter cells. Before we can begin to understand what meiosis is however, we need to review some basic terminology of genetics.