Final Study Guide Anatomy PhysiologyCell Organization

All living things are made of one or more cells. Cells are the basic building blocks of all organisms. The organization of cells into complex structures allows for the wide variety of life found in multicellular organisms.

Organization in Multicellular OrganismsFrom simplest to most complex, the proper levels of organization in multicellular organisms are:

The levels of biological organization in order from smallest to largest are:

organelle → cell → tissue → organ → organ system → whole organism.

Organelles

Organelles are specialized subunits in the cell, which each have their own specific function. They are usually enclosed in their own lipid membrane. There are many types of organelles, such as ribosomes, nuclei, endoplasmic reticulum, and lysosomes.

Cells

Cells are the structural and functional units of all living organisms. Organisms can be made up of one cell, like bacteria, or many cells, like animals. Cells specialize depending upon which part of the body they are located. All cells come from other cells, and they divide by mitosis or meiosis. Cells contain organelles and the genetic information of an organism.

Tissues

Tissues are composed of many cells that work together to perform a specific function. Tissue covers most parts of an organism. There are several types of tissues, such as connective tissue, muscle tissue, nervous tissue, and epithelial tissue.

Organs

Organs are composed of several tissues and perform one or more functions in the body. In most organs there is a unique 'main' type of tissue (such as the myocardium of the heart) and several other tissues that are found in many organs (such as connective tissue). The body is made up of many organs, including the heart, lungs, liver, eyes, and brain.

Organ Systems

Organ systems are groups of related organs that work together to perform a function or set of functions. The functions of the various organ systems usually overlap and are influenced by each other. There are eleven major organ systems in the human body, including the respiratory, reproductive, digestive, skeletal, muscular, nervous, circulatory, endocrine, urinary, integumentary, and lymphatic systems. There are two main organ systems in vascular plants—the root system and the shoot system.

Whole Organism

The whole organism is composed of all of the various organ systems. Its functions are carried out by cooperation between all of the systems.

Reproductive SystemThe reproductive system controls certain hormones in the human body, which keep the body healthy and able to reproduce.

Female Reproductive SystemThe human female reproductive system includes several organs, and is designed to perform functions such as:

producing gametes in the ovaries

production of hormones such as estrogen and progesterone

supporting the development of a fetus in the uterus

providing essential materials through the placenta

providing nutrition, or milk, from the mammary glands

Cervix

The cervix is the low, narrow section of the uterus which joins to the top of the vagina. During the monthly menstruation cycle, the cervix is stretched to allow the shedding of the endometrium. During childbirth, the cervix stretches, or dilates, to allow the child to pass through.

Endometrium

The endometrium is the inner membrane of the uterus. During the menstrual cycle, the endometrium becomes thick and blood-rich. If an egg is not implanted into the uterine wall, the endometrium is then shed, resulting in menstruation.

Fallopian Tube

The fallopian tubes are two fine tubes that are lined with ciliated epithelium and connect the ovaries to the uterus. When an ovary releases an egg, it travels through the fallopian tube and into the uterus.

Mammary Gland

The mammary glands are organs that produce milk in the breasts of females. The milk is used to help nourish a newborn baby.

Ovary

Ovaries are egg-producing organs that usually occur in pairs in the female body. They are attached to the fimbria of the fallopian tube. Eggs produced in the ovary travel through the fallopian tube and into the uterus. Usually, each ovary takes turns producing an egg each month.

Uterus

The uterus, or womb, is a pear-shaped organ that accepts fertilized eggs from the fallopian tubes. A fertilized egg implants into the wall of the uterus, where a rich supply of blood helps to nourish the egg’s development. The uterus is where the developing fetus remains until birth.

Placenta

The placenta is an organ attached to the wall of the uterus that develops from the same egg and sperm cells that fused to form the fetus. The fetus is connected to the placenta by an umbilical cord, through which nutrients from the mother are provided, gases are exchanged, and waste is removed.

Vagina

The vagina is the muscular tract that leads from the uterus to outside the body. During childbirth, the baby travels from the uterus and the vagina to be born.

Male Reproductive SystemThe human female reproductive system includes several organs, and is designed to perform functions such as:

producing gametes in the testes

delivery of gametes for fertilization

production of hormones such as testosterone

Penis

The penis is used to allow urine and semen to leave the body. It is made up of two parts—the shaft and the glans. The shaft is the main part of the penis, which is composed of spongy tissue. The glans is the tip, where semen and urine exit the body through the urethra.

Prostate Gland

The prostate gland secretes a fluid that nourishes the sperm. It also produces fluids that lubricate the duct system and make up part of the semen. The gland surrounds ejaculatory ducts and sits at the base of the urethra.

Scrotum

The scrotum is a muscular sac that holds the testes. It functions to keep the testes at a slightly lower temperature than the rest of the body.

Testes

The testes are two oval shaped structures that produce and store sperm and the hormone testosterone. The testes are held in the scrotum.

Urethra

The urethra is a tube that connects the urinary bladder and the ejaculatory ducts to the outside of the body. Both urine and semen are transported through this tube.

Human DevelopmentEvery human begins as a single cell. During the nine months of gestation—the period of development that an offspring undergoes while inside its mother's body—one cell grows into the trillions of cells of hundreds of different kinds that make up the human body.

The human gestation period is forty weeks, measured from the time of the mother's last menstrual period, or 38 weeks, measured from the time of conception. The human gestation period is typically divided into  trimesters.

ConceptionThe first cell containing all of the genetic material of a new human is created by fertilization when the father's sperm and the mother's ovum combine to create a new, unique genetic code.

Image courtesy of www.PDImages.com.

Cell growth and division begins immediately as the fertilized egg moves toward the uterus, where it will implant in the uterine lining that the mother's body has prepared to nourish and protect it.

Sometimes the word conception is used to refer to the entire process up to and including implantation; other times it refers only to the fusion of the chromosomes of the ovum and sperm.

Human Growth & DevelopmentHumans progress through many stages of development during their lifetimes.

After fertilization, humans begin as a zygote before developing into an embryo and later into a fetus.

After birth, humans begin as infants before developing into toddlers and progressing through childhood, adolescence, and adulthood.

Early LifeIn humans, the male reproductive system produces gametes called sperm, and the female reproductive system produces gametes called eggs. A sperm and egg fuse during the process of fertilization. Fertilization occurs inside a female's fallopian tube.

Once the egg is fertilized, it becomes a new type of cell called a zygote. A zygote is a cell that is capable of developing into a new human being. A zygote has a full set of DNA— half was received from the mother and half was received from the father.The zygote travels down the fallopian tube to the female's uterus. During this journey, the zygote undergoes cell division many times and becomes an embryo. An embryo is an organism in the earliest stage of its development.When the embryo reaches the uterus, it implants itself in the uterine wall. Over the course of nine months, the embryo develops into a fetus. Then, the mother will give birth to the fetus.Birth is the process in which a fetus leaves its mother's body.

Life Following BirthWhen a fetus is born, it is an infant. An infant is a human being in its earliest stage of life. Infancy lasts from birth to one year of age. Over that first year of life, the infant grows rapidly and becomes more coordinated.After one year, infants develop into toddlers before entering childhood, adolescence, and finally adulthood.

The Cardiovascular SystemThe cardiovascular system  is composed of the heart, arteries, capillaries and veins. The circulatory system transports blood that is low in oxygen from the body to the lungs and heart through veins, and it transports oxygenated blood from the lungs and heart throughout the body through arteries.

Components of the Cardiovascular SystemThe major components of the cardiovascular system include the heart, veins, arteries, and capillaries. In the following diagram, illustrates the distribution of blood vessels throughout the human body. Veins are shown in blue, and arteries are represented in red.

Adapted from image courtesy of Wikipedia

The heart is made up of four chambers. Two of them, the right atrium and the right ventricle, push blood returning from the body to the lungs. The other two, the left atrium and the left ventricle, receive blood, rich in oxygen from the lungs, and send it back out to the body.Veins are the larger blood vessels that carry blood back to the heart after its oxygen has been delivered to body tissues. Veins are normally drawn blue in diagrams.Arteries move blood that is rich in oxygen away from the heart. The pressure from the heart's pumping action keeps this blood moving in the right direction. Arteries are normally drawn red in diagrams.Capillaries are tiny blood vessels that deliver oxygen to tissues. They can only be seen under a microscope because they are about one-tenth the width of a human hair. Capillaries have thin walls that allow oxygen and nutrients from the blood to move through them to the tissues. Carbon dioxide and other wastes leave the body

cells, cross through the capillary walls, and enter the blood for the trip back to the heart and lungs.

The Nervous SystemThe nervous system gathers, interprets, and responds to information about the body's internal and external environment.

Major Components of the Nervous SystemThe nervous system consists of the brain, the spinal cord, and nerve cells. These parts work together to communicate with the other organ systems, controlling and directing the activities and actions of the human body.

Nerve cells have long axons, or filaments, that extend throughout the body. These nerve cells receive information from the environment and send it through the spinal cord and to the brain. The brain then processes the information and determines the appropriate response.The spinal cord relays information to and from the brain. Nerves extend from the spinal cord to the rest of the body. The spinal cord is protected by the spinal column, which is composed of vertebrae.The brain is the control center of the body, which directs bodily functions and helps humans to respond to events. The brain controls all of the functions of the body.

When the senses (sight, smell, touch, taste, hearing) are used, organs send information to the brain using the nervous system's pathways.

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The Immune SystemThe  immune system  is a network of cells, tissues, and organs that defends the body against foreign invaders as well as some internal threats.

Immune responses can be either specific or nonspecific.

Threats to Health & HomeostasisThere are many potentially harmful invaders, or pathogens, that can disrupt the normal functioning of the body. These include bacteria and viruses (often called germs), fungi, and parasites. The immune system functions to both defend against such pathogens and mount a coordinated attack against them if infection occurs.At other times, the threat may come from within the body itself. For example, cancer is a condition in which some of the body's cells multiply uncontrollably. The immune system is equipped to fight these problems as well.

In both cases, the body may not be able to completely destroy the threat, and medicines or other therapies may be required to reinforce or complement the body's natural immune system.

Bacteria, viruses, fungi, and parasites are all potential pathogens.

Components of the Immune SystemThe immune system is made up of an extensive network of cells, tissues, and organs. Bone marrow, a soft tissue found inside the long bones, produces the body's red and white blood cells. Leukocytes, or white blood cells, are the key players in the immune system.Two organs that participate in the immune system, the thymus and spleen, also have the ability to produce and store different types of leukocytes.The lymphatic system, seen here as a network of lymph nodes and vessels, can transport (via vessels) and store (via nodes) large amounts of white blood cells when the body is responding

Nonspecific Immune ResponseSeveral physical barriers, such as the skin, mucus, and hair, serve as a first line of defense and prevent most pathogens from entering the body. If a barrier is penetrated, however, infection can result. There are five main ways in which infectious agents may enter the body:

through damaged skin

inhalation

ingestion

transmission through body fluids during sexual activities

transmission from a mother to her baby during pregnancy or birth

Once inside the body, foreign pathogens encounter the body's second line of defense, the nonspecific (innate) immune response. Circulating white bloods cells called phagocytes patrol the body in search of pathogens, infected or damaged body cells, and even some cancer cells. Once a target is found, the phagocyte literally engulfs and digests it through phagocytosis. This process is being performed in the picture by a macrophage as it extends its pseudopodia ("arms") to engulf two foreign bodies. Neutrophils, the most abundant phagocytes, also possess granules containing lethal chemicals that can be released directly into their targets.If infection continues despite the actions of phagocytes, a general inflammatory response may occur. An inflammatory response is often marked by fever, where the body

raises its temperature to a level at which many pathogens are either inactivated or killed. The higher body temperature also allows enzymatic reactions of the immune response to occur more quickly and optimizes production of more white blood cells. In some cases, certain leukocytes release chemicals, like histamine, that cause increased mucus production, sneezing, coughing, and watery eyes in order to trap and rid the body of pathogens. Vomiting and diarrhea are also ways in which the body expels pathogens, though they aren't specifically tied to an immune response.

The innate immune response is considered nonspecific because it is able to respond to a wide range of foreign agents without producing any specialized white blood cells.

Specific Immune ResponseIf the infection or threat is not resolved during the innate response, the third and final line of defense is initiated. The specific immune response produces cells specifically tailored to kill the foreign invader.

First, a phagocyte (e.g., a macrophage) encounters a pathogen and engulfs it. It then displays the antigen—the protein component of the pathogen that identifies it as foreign—on its own surface. This display stimulates a special class of white blood cells called lymphocytes to mobilize. Lymphocytic T cells, produced by the thymus, respond by either becoming cytotoxic (killer) T cells or helper T cells. Cytotoxic T cells find and destroy any infected cells that display the target antigen. Meanwhile, helper T cells signal B cells (derived from bone marrow) to be on the lookout for the pathogen. As seen in the picture, once the B cell encounters the pathogen, it is activated and begins to multiply. Most of the resulting cells become plasma cells and produce antibodies that attach to any infected cells and mark them for mass destruction by a

rapidly dividing army of phagocytes. A few others become memory cells that retain the ability to recognize the pathogen if it ever enters the body again.

Memory cells are vital to the actions of the specific immune response because, upon subsequent contact with a pathogen it has previously fought, the immune system will be able to react much more quickly. Often, this means that the pathogen will be destroyed before it can make the person sick again, resulting in partial (and sometimes permanent) immunity.

The levels of cellular organization can be summarized from least complex to most complex by the following diagram:

Cell parts are specialized subunits in the cell. They are usually enclosed in their own lipid membrane, and they each have their own specific function. There are many types of cell parts, such as ribosomes, nuclei, mitochondria, and chloroplasts.Cells are the fundamental unit of life. They are the most basic structure in the organizational chart shown above.Tissues make up the second level of organization. Tissues are made up of groups of similar cells that work together to perform specialized functions. Examples of specific kinds of tissue are muscle tissue, nervous tissue, and epithelial tissue. Each type of tissue has a specialized function within an organism's body.Organs are the third level of organization. An organ is a group of tissues that work together to perform a specific function. Unlike tissue, organs can be made of many different kinds of specialized cells because they are a combination of different kinds of tissue. Examples of human organs include the heart, the brain, the liver, the stomach, and the kidneys, as well as many other structures.Organ systems are the fourth level of organization. Organ systems are composed of organs with interrelated functions. For example, the urinary system is an organ system made up of organs that produce, store, and carry urine.Organisms are the highest level of cellular organization and represent complete living systems, such as plants and animals.

Human Body SystemsThe human body is made of many different organ systems. Each system performs unique functions for the body, but the systems also interact with each other to perform more complex functions.

Major Organ Systems

In humans, cells, tissues, and organs group together to form organ systems. These systems each perform different

functions for the human body.

Some of the major organ systems and their functions in humans include:

The Nervous System — The nervous systems consists of two parts. The central nervous system consists of the brain and spinal cord, while the peripheral nervous system includes all other nervous tissue. The nervous system gathers, interprets, and responds to information about the body's internal and external environment. The smallest unit of the nervous system is the nerve cell, or neuron. Neurons communicate with each other and with other cells by producing and releasing electrochemical signals known as nerve impulses.

The Circulatory System — The circulatory (or cardiovascular) system is composed of the heart, arteries, veins, and capillaries. The circulatory system is responsible for transporting blood to and from the lungs so that gas exchange can take place. As the circulatory system pumps blood throughout the body, dissolved nutrients and wastes are also delivered to their destinations.

The Respiratory System — The main structures of the respiratory system are the trachea (windpipe), the lungs, and the diaphragm. When the diaphragm contracts, it creates a vacuum in the lungs that causes them to fill with air. During this inhalation, oxygen diffuses into the circulatory system while carbon dioxide diffuses out into the air that will be exhaled.

The Digestive System — The digestive system is responsible for taking in food, digesting it to extract energy and nutrients that cells can use to function, and expelling the remaining waste material. Mechanical and chemical digestion takes place in the mouth and stomach, while absorption of nutrients and water takes place in the intestines.

The Skeletal System — The skeletal system is made up of over 200 bones. It protects the body's internal organs, provides support for the body and gives it shape, and works with the muscular system to move the body. In addition, bones can store calcium and produce red and white blood cells.

The Muscular System — The muscular system includes more than 650 tough, elastic pieces of tissue. The primary function of any muscle tissue is movement. This includes the movement of blood through the arteries, the movement of food through the digestive tract, and the movement of arms and legs through space. Skeletal muscles relax and contract to move the bones of the skeletal system.

The Excretory System — The excretory system removes excess material, dangerous substances, and other waste materials from the body. The human excretory system includes the lungs, sweat glands in the skin, and the urinary system (i.e. the kidneys and the bladder).

The Endocrine System — The endocrine system is involved with the control of body processes such as fluid balance, growth, and sexual development. The endocrine system controls these processes through hormones, which are produced by endocrine glands. Some endocrine glands include the pituitary gland, thyroid gland, parathyroid gland, adrenal glands, thymus gland, ovaries in females, and testes in males.

The Immune System — The immune system is a network of cells, tissues, and organs that defends the body against foreign invaders. The immune system uses antibodies and specialized cells, such as T-cells, to defend the body from microorganisms that cause disease.

The Reproductive System — The reproductive system includes structures, such as the uterus and fallopian tubes in females and the penis and testes in males, that allow humans to produce new offspring. The reproductive system also controls certain hormones in the human body that regulate the development of sexual characteristics and determine when the body is able to reproduce.

The Integumentary System — The integumentary system is made up of a person's skin, hair, and nails. The skin acts as a barrier to the outside world by keeping moisture in the body and foreign substances out of the body. Nerves in the skin act as an interface with the outside world, helping to regulate important aspects of homeostasis, such as body temperature.

Interacting Organ SystemsAll living organisms must be able to maintain a stable internal environment, or homeostasis. In order to achieve this stability, organ systems must interact with one another. The following list provides examples of how interacting organ systems work together to perform a task.

Using Energy

Food is taken in and broken down by the digestive system. The raw materials diffuse into the blood and are transported to cells in the rest of the body by the circulatory system. The leftover solid waste exits the body through the digestive system.

Exchanging Gases

As blood circulates throughout the body, it picks up carbon dioxide waste from cells and transports it to the lungs. When blood circulates through the lungs, carbon dioxide is replaced with oxygen that was inhaled, or breathed in, from the air. The carbon dioxide is then removed from the body when the lungs exhale, or breath out.

Eliminating Cellular Waste

Cells produce waste materials as part of their living processes. These wastes are soluble, so they can be transported within fluids. When cells release wastes, they are collected in the blood and carried through the circulatory system to the kidneys. The kidneys, which are part of the urinary system, filter dissolved wastes from the blood. The wastes are stored in the bladder in the form of urine until they can be excreted from the body.

Producing Movement

Muscles often work in pairs to move bones along a joint. For example, when the biceps muscle in the front of the upper arm tightens or contracts, the triceps in the back of the upper

arm relaxes so that the arm can bend at the elbow. To straighten the arm back out, the triceps muscle contracts and the biceps muscle relaxes.

Sustaining Activity

When a person is participating in heavy activity, the nervous system first sends messages to the circulatory and respiratory systems. The breathing rate is increased in order to take in more oxygen. The heart rate increases in order to circulate the oxygen carried by the blood to cells all over the body. Cells use the oxygen to create energy needed for activities. In particular, muscle cells need oxygen to move in response to messages received from the nervous system.