Pdf For Human Anatomy And Physiology
Violet Mcdow
The human body exhibits a variety of movements from walking and running to crawling, jumping and climbing. The framework that enables us to do all these activities is the skeleton. Humans have as much as 300 bones at birth. However, the bones start to fuse with age. At adulthood, the total number of bones is reduced to 206.
Joints are the points at which two or more bones meet. They enable a range of movements like rotation, abduction, adduction, protraction, retraction and more. Based on flexibility and mobility, joints can be further classified into movable joints and immovable joints. Movable joints are flexible while immovable joints (also called fixed joints) are non-flexible since the bones are fused.
Muscles are specialised tissues which assist the bones in locomotion. Muscles are attached to the bones through tendons. Movement of limbs happens due to the contraction and relaxation of the corresponding muscles present in that region. Joints help in the flexibility of bones, but a bone cannot be bent or stretched until a muscle acts on it. In other words, the muscles attached to that bone pulls it to the direction of movement.
Furthermore, most movement involves muscles that work as a pair. For example, when we bend our arm, muscles in that region contract, become shorter and stiffer and pull the bones to the direction of movement. For relaxation (stretching), muscles in the opposite direction have to pull the bones towards it.
Humans have evolved separately from other animals, but since we share a distant common ancestor, we mostly have a body plan that is similar to other organisms, with just the muscles and bones in different proportions.
For example, we might assume giraffes have more vertebrae in its neck than humans. No, despite being incredibly tall, giraffes have the same number of vertebrae, i.e. they also have seven vertebrae in their neck.
This is the result of humans having ancestors that began walking on their hind limbs rather than using all four limbs. Most of our anatomical insight was gained through the dissection of corpses (cadavers), and for a long time, it was the only way we could gain anatomical knowledge about the human body. It was a rather grotesque affair, but it made up the bulk of medical literature for centuries. These days, technological innovation has made it possible to explore human anatomy at a microscopic level.
Even to this day, scientists are newly discovering organs that were previously overlooked or have been mistakenly identified as other existing tissues. In 2018, scientists had discovered a new, body-wide organ called the Interstitium that exists right under the skin.
It is referred to the physical, mechanical, and biochemical function of humans. This connects health, medicine, and science in a way that studies how the human body acquaints itself to physical activity, stress, and diseases.
And out of these 79 organs, five are crucial for survival, and any damage to these five organs might result in termination of life. These five crucial human body parts are the brain, heart, liver, lungs and kidneys. Read on to explore more about these body parts and their functions in detail:
The circulatory system is also referred to as the cardiovascular system. It comprises the heart and all the blood vessels: arteries, capillaries, and veins. There are essentially two components of circulation, namely:
The process of digestion starts with mastication (chewing food). Then, the saliva mixes with food and forms a bolus, a small rounded mass that can be easily swallowed. Once swallowed, the food travels down the oesophagus and into the stomach. The stomach secretes strong acids and powerful enzymes that break the food down into a paste.
It then moves into the small intestine where the food is broken down even more because of the bile secreted by the liver and powerful, digestive enzymes from the pancreas. This is the stage at which nutrients are absorbed from the food.
The leftover materials (stool) then move on to the large intestine where it transforms from liquid to solid, as water is removed. Finally, it gets pushed into the rectum, ready to be eliminated from the body.
The human reproductive system is also known as the genital system that comprises internal and external organs that help in reproduction. It varies for both males and females. Hormones, fluids, and pheromones are all connective accessories for the reproductive organs to function.
Also known as the womb, the uterus is a pear-shaped organ where the fetus grows. The cervix is the route to the vagina and gateway for sperm to enter. Vagina acts as the route for a penis to enter during intercourse and the exit of the fetus during delivery.
The respiratory process involves the intake of oxygen, and the exhale of carbon dioxide from the body. This system is also known as the ventilatory system, gas exchange system or respiratory apparatus. Vertebrates like human beings possess lungs for respiration. The process of respiration starts with the cycle of inhalation and exhalation.
The voluntary and involuntary actions are maintained and taken care of by the central nervous system. It helps to channel the signals to and from different parts of our body. Nervous System is broadly classified into two categories:
The central nervous system contains the brain and the spinal cord, while the peripheral nervous system includes nerves and ganglia that are present outside the brain and spinal cord. Through the axons, every part of the body gets connected.
Every human being, tissues, human body parts and the organ systems are made up of cells- the fundamental unit of life. Anatomy is the science of understanding the structure and the parts of living organisms. Physiology, on the other hand, deals with the internal mechanisms and the processes that work towards sustaining life.
These can include biochemical and physical interactions between various factors and components in our body. With the progress of evolution, organisms began to exhibit advanced characteristics and features that enabled them to be more efficient and thrive in their respective environment.
The human structure can be described as bipedal, with hair covering the body, presence of mammary glands and a set of extremely well-developed sense organs. With respect to human body anatomy, we have a specialized circulatory system that enables the efficient transport of materials and nutrients within the body.
The presence of a well-developed digestive system helps to extract essential nutrients and minerals required by the body. A well developed respiratory system ensures the efficient gas exchange and the nervous system enables coordination and interaction within the body and also the external environment, thereby ensuring survival.
The external human body consists of a head, hair, neck, torso (which includes the thorax and abdomen), genitals, arms, hands, legs, and feet. The internal human body includes organs, teeth, bones, muscle, tendons, ligaments, blood vessels and blood, lymphatic vessels and lymph.
The study of the human body includes anatomy, physiology, histology and embryology. The body varies anatomically in known ways. Physiology focuses on the systems and organs of the human body and their functions. Many systems and mechanisms interact in order to maintain homeostasis, with safe levels of substances such as sugar, iron, and oxygen in the blood.
The adult male body is about 60% total body water content of some 42 litres (9.2 imp gal; 11 US gal). This is made up of about 19 litres (4.2 imp gal; 5.0 US gal) of extracellular fluid including about 3.2 litres (0.70 imp gal; 0.85 US gal) of blood plasma and about 8.4 litres (1.8 imp gal; 2.2 US gal) of interstitial fluid, and about 23 litres (5.1 imp gal; 6.1 US gal) of fluid inside cells.[1] The content, acidity and composition of the water inside and outside cells is carefully maintained. The main electrolytes in body water outside cells are sodium and chloride, whereas within cells it is potassium and other phosphates.[2]
The body contains trillions of cells, the fundamental unit of life. At maturity, there are roughly 30 trillion cells, and 38 trillion bacteria in the body,[3][4] an estimate arrived at by totaling the cell numbers of all the organs of the body and cell types. The skin of the body is also host to billions of commensal organisms as well as immune cells.[5] Not all parts of the body are made from cells. Cells sit in an extracellular matrix that consists of proteins such as collagen, surrounded by extracellular fluids.
Cells in the body function because of DNA. DNA sits within the nucleus of a cell. Here, parts of DNA are copied and sent to the body of the cell via RNA.[6] The RNA is then used to create proteins, which form the basis for cells, their activity, and their products. Proteins dictate cell function and gene expression, a cell is able to self-regulate by the amount of proteins produced.[7] However, not all cells have DNA; some cells such as mature red blood cells lose their nucleus as they mature.
The body consists of many different types of tissue, defined as cells that act with a specialised function.[8] The study of tissues is called histology and is often done with a microscope. The body consists of four main types of tissues. These are lining cells (epithelia), connective tissue, nerve tissue and muscle tissue.[9]
Organs, structured collections of cells with a specific function,[10] mostly sit within the body, with the exception of skin. Examples include the heart, lungs and liver. Many organs reside within cavities within the body. These cavities include the abdomen (which contains the stomach, for example) and pleura, which contains the lungs.
The heart is an organ located in the thoracic cavity between the lungs and slightly to the left. It is surrounded by the pericardium, which holds it in place in the mediastinum and serves to protect it from blunt trauma, infection and help lubricate the movement of the heart via pericardial fluid.[11] The heart works by pumping blood around the body allowing oxygen, nutrients, waste, hormones and white blood cells to be transported.
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