different types of cells in the human body and their functions pdf

Different types of cells in the human body and their functions pdf

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Topics in the How Genes Work chapter

For more information about cells:

What is a cell?

This photo looks like a close-up of an old-fashioned dust mop, and the object it shows has a somewhat similar function. However, the object is greatly enlarged in the photo. Can you guess what it is? The answer may surprise you. It is a scanning electron micrograph of human epithelial cells that line the bronchial passages.

Topics in the How Genes Work chapter

This photo looks like a close-up of an old-fashioned dust mop, and the object it shows has a somewhat similar function. However, the object is greatly enlarged in the photo. Can you guess what it is? The answer may surprise you. It is a scanning electron micrograph of human epithelial cells that line the bronchial passages. The floppy, dust-mop-like extensions are actually microscopic structures called cilia projecting from the outer surface of the epithelial cells. The function of the cilia is to trap dust, pathogens, and other particles in the air before it enters the lungs.

The cilia also sway back and forth to sweep the trapped particles upward toward the throat, from which they can be expelled from the body. Like the ciliated bronchial cells in the micrograph above, many other cells in the human body are very distinctive and well suited for special functions. To perform their special functions, cells may vary in a number of ways. Some cells act as individual cells and are not attached to one another.

Red blood cells are a good example. Their main function is to transport oxygen to other cells throughout the body, so they must be able to move freely through the circulatory system. Many other cells, in contrast, act together with other similar cells as part of the same tissue, so they are attached to one another and cannot move freely. For example, epithelial cells lining the respiratory tract are attached to each other to form a continuous surface that protects the respiratory system from particles and other hazards in the air.

Many cells can divide readily and form new cells. Skin cells are constantly dying and being shed from the body and replaced by new skin cells, and bone cells can divide to form new bone for growth or repair.

Some other cells, in contrast, such as certain nerve cells, can divide and form new cells only under exceptional circumstances. Many human cells have the primary job of producing and secreting a particular substance, such as a hormone or an enzyme. For example, special cells in the pancreas produce and secrete the hormone insulin, which regulates the level of glucose in the blood. Some of the epithelial cells that line the bronchial passages produce mucus, a sticky substance that helps trap particles in the air before it passes into the lungs.

All the different cell types within an individual human organism are genetically identical, so no matter how different the cells are, they all have the same genes. How can such different types of cells arise? The answer is the differential regulation of genes. Cells with the same genes can be very different because different genes are expressed depending on the cell type. Many common types of human cells — such as bone cells and white blood cells — actually consist of several subtypes of cells.

Each subtype, in turn, has a special structure and function. A closer look at these cell types will give you a better appreciation for the diversity of structures and functions of human cells. There are four main subtypes of bone cells, as shown in the diagram below. Each type has a different form and function:. White blood cells also called leukocytes are even more variable than bone cells. Five subtypes of white blood cells are shown in the figure below.

All of them are immune system cells involved in defending the body, but each subtype has a different function. They also differ in the normal proportion of all leukocytes they make up. Groups of connected cells form tissues. The cells in a tissue may all be the same type or they may be of multiple types.

In either case, the cells in the tissue work together to carry out a specific function. There are four main types of human tissues: connective, epithelial, muscle, and nervous tissues. The most diverse and abundant of all tissues, connective tissue holds cells together and supports the body. Connective tissue is made up of cells suspended in a non-cellular matrix.

The matrix also known as ground substance is secreted by the connective tissue cells and determines the characteristics of the connective tissue. It is the consistency of the matrix that determines the function of the connective tissue.

The matrix can be liquid, gel-like or solid, all depending on the type of connective tissue. For example, the extracellular matrix of bone is a rigid mineral framework. The extracellular matrix of blood is liquid plasma. Connective tissues such as bone and cartilage generally form the body's structure. It stores fat for energy and provides insulation. CC BY 3. This is a loose connective tissue made up of a network of reticular fibers that provides a supportive framework for soft organs.

Dense connective tissue proper : This tissue consists of three categories, dense regular connective tissue, dense irregular connective tissue, and elastic connective tissue. These tissues differ on the arrangement and composition of the fibrous elements of the extracellular matrix.

The osteon, osteocytes, central Haversian canal, and canaliculi are visible. Bone : A hard, mineralized tissue found in the skeleton. The bone matrix contains many collagen fibers as well as inorganic mineral salts, calcium carbonate, and calcium phosphate, all features that make it a very rigid structure. Bone cells, called osteoblasts , secrete the osteoid substance that eventually hardens around the cells to form an ossified matrix. The osteon forms the basic unit of compact bone. Within the osteon, the osteocytes mature bone cells are located in lacunae.

Because the bone matrix is very dense, the osteocytes get their nutrition from the central canal via tiny canals called canaliculi. The fluid matrix is called plasma, and formed elements of this tissue include white blood cells, red blood cells, and platelets. Read more about the composition and function of blood in the cardiovascular system chapter.

Epithelial tissue is made up of cells that line inner and outer body surfaces, such as the skin and the inner surface of the digestive tract. Epithelial tissue that lines inner body surfaces and body openings is called mucous membrane. This type of epithelial tissue produces mucus , a slimy substance that coats mucous membranes and traps pathogens, particles, and debris. Epithelial tissue protects the body and its internal organs, secretes substances such as hormones in addition to mucus, and absorbs substances such as nutrients.

Most epithelial tissue is described with two names. The first name describes the number of cell layers present and the second describes the shape of the cells. One layer of epithelial cells is called simple and more than one layer of epithelial cells is called stratified.

There are three basic shapes of the epithelial cells, squamous, cuboidal, and columnar. Squamous cells are thin and flat; cuboidal cells have a shape of a cube; columnar cells have a shape of a pillar. For example, simple squamous epithelial tissue describes a single layer of cells that are flat and scale-like in shape.

Muscle tissue is made up of cells that have the unique ability to contract or become shorter. There are three major types of muscle tissue, as pictured below: skeletal, smooth, and cardiac muscle tissues. Neurons transmit electrical messages and the other cells play supporting roles. Nervous tissue makes up the central nervous system mainly the brain and spinal cord and peripheral nervous system the network of nerves that runs throughout the rest of the body.

There are four types of nervous tissues:. If you are a blood donor, then you have donated tissue. Blood is a tissue that you can donate when you are alive. Deceased people can donate many different tissues, including skin, bone, heart valves, and the corneas of the eyes. If you are not already registered as a tissue donor, the information below may help you decide if you would like to register.

Each year, approximately 30, people donate tissues, which supply tissues for up to 1 million tissue transplants. One tissue donor can enhance or save the life of more than 50 people! Unlike organs, which generally must be transplanted immediately after the donor dies, donated tissues can be processed and stored for a long time for later use. Donated tissues can be used to replace burned skin and damaged bone and to repair ligaments. Corneal tissues can be used for corneal transplants that restore sight in blind people.

In fact, each year 48, patients have their sight restored with corneal transplants. Unfortunately, there are not enough tissues to go around, and the need for donated tissues keeps rising. Why are mucous membranes often located in regions that interface between the body and the outside world?

Dust Mop This photo looks like a close-up of an old-fashioned dust mop, and the object it shows has a somewhat similar function. Human Cells Like the ciliated bronchial cells in the micrograph above, many other cells in the human body are very distinctive and well suited for special functions. Variation in Human Cells Some cells act as individual cells and are not attached to one another.

Different but Identical All the different cell types within an individual human organism are genetically identical, so no matter how different the cells are, they all have the same genes. Examples of Human Cell Types Many common types of human cells — such as bone cells and white blood cells — actually consist of several subtypes of cells. Bone Cells There are four main subtypes of bone cells, as shown in the diagram below.

Each type has a different form and function: Osteocytes are star-shaped bone cells that make up the majority of bone tissue. They are the most common cells in mature bone and can live as long as the organism itself.

They also control the function of bone cells called osteoblasts and osteoclasts. Osteoblasts are cells with single nuclei that synthesize new bone. They function in organized groups of connected cells called osteons to form the organic and mineral matrix of bone.

Osteogenic cells are undifferentiated stem cells that differentiate to form osteoblasts in the tissue that covers the outside of the bone.

For more information about cells:

The heart pumps blood through the arteries, capillaries and veins to provide oxygen and nutrients to every cell of the body. The blood also carries away waste products. The adult human body contains approximately 5 liters of blood. It makes up 7 to 8 percent of a person's body weight. Approximately 2. Plasma is the liquid portion of the blood. Blood cells like red blood cells float in the plasma.

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Transformative technologies are enabling the construction of three-dimensional maps of tissues with unprecedented spatial and molecular resolution.

Cells are the basic building blocks of all living things. The human body is composed of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialized functions. Cells have many parts, each with a different function. Some of these parts, called organelles, are specialized structures that perform certain tasks within the cell. Human cells contain the following major parts, listed in alphabetical order:.


There are about different kinds of specialized cells in the human body. body. • Epithelial cells: Functions of epithelial cells include secretion, absorption,​.


What is a cell?

Cells in the human body number in the trillions and come in all shapes and sizes. Cells comprise tissues , tissues make up organs, organs form organ systems , and organ systems work together to create an organism and keep it alive. Each type of cell in the human body is specially equipped for its role. Cells of the digestive system , for instance, are vastly different in structure and function from cells of the skeletal system.

Types of Cells in the Human Body

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5 comments

  • Jairo R. 04.06.2021 at 21:15

    It contains various types of information, such as cell morphologies, gene expression and literature references.

    Reply
  • Eleanor L. 05.06.2021 at 09:48

    Proteins are large, complex molecules that play many critical roles in the body.

    Reply
  • Bart V. 10.06.2021 at 20:29

    Humans are multicellular organisms with various different types of cell varies based on the type of cell and its location in the human body.

    Reply
  • Enlesliacurt 11.06.2021 at 02:34

    Essays in english on current topics in india pdf the moral revolution in atlas shrugged pdf

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  • Sexy3636 11.06.2021 at 05:51

    There are over different cell types in the human body. Each type of cells is specialised to carry out a particular function, either solely, but usually by forming a.

    Reply

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