Lesson Video: Specialized Cells | Nagwa Lesson Video: Specialized Cells | Nagwa

Lesson Video: Specialized Cells Biology

In this video, we will learn how to recall different specialized cells, describe their adaptations and relate these adaptations to their functions.


Video Transcript

In this video, we will learn how to recall different specialized cells, describe their adaptations, and relate these adaptations to their functions. So let’s make like a muscle cell contracting and get started.

First, let’s recall that the cell is the basic unit of life or the smallest thing that can be considered to be independently alive. A group of cells that work together to perform a specific function are called a tissue. A group of tissues that work together to carry out a function are called an organ. Several different organs that work together to carry out a specific function are called an organ system. And most multicellular organisms contain several different organ systems.

When you see a diagram of a cell, it’s usually generalized or simplified. But the actual cells in our body are specialized. When we say that a cell is specialized, we mean that it has specific adaptations that help it to carry out its job. Or to state things a little more simply, its form follows its function.

The word “form” refers to the structure of an object, its shape and its parts, while “function” refers to what a thing does or what its specific job is. An analogy to specialized cells can be found in the specialized materials used to build a house. This image is a generalized house. Like our generalized cell, it’s simplified and represents many different houses. However, it’s made of parts that are specialized, different materials that have specific traits that allow them to carry out a specific job.

The bricks of this house give the walls their structure and their shape. The transparent windows allow the occupants to see out and also let light into the house. The wiring carries electricity, and so on and so forth. Each different part has its own specific job. In a house, it’s important that each part match with its function, just like the cells of a living organism. If we built the windows out of bricks instead of transparent glass, they would no longer function as windows because their form would be so drastically different.

In the same way, the cells of our bodies have a form or a shape and structure that’s specific to the job that they carry out biologically. So when we say that a cell is specialized, we mean that its form is specific to its function in the same way that glass is specific to the function of windows. And unlike building materials, when we’re talking about the form of a cell, we’re referring specifically to its size, its shape, and its subcellular structures.

So next, we’ll take a look at several examples of human cells and look closely at how their form supports their function.

We’ll start with red blood cells, also called erythrocytes. These cells are quite small in comparison with other cells of your body, although they’re very numerous. They have a flattened, concave, disk-like shape, which is due to the fact that mature red blood cells do not possess a nucleus. These cells also lack mitochondria as well as most other organelles. They’re basically just sacs filled with cytoplasm that’s rich in hemoglobin.

Hemoglobin is a large iron-containing protein which is able to transport oxygen. And transporting oxygen is the primary function of the red blood cells. These cells are responsible for carrying oxygen from the lungs to the tissues of the rest of the body, where it’s used in cellular respiration to generate cellular energy. The size, shape, and subcellular structures of red blood cells give them special properties, which make them perfectly adapted to their function of carrying oxygen throughout the blood vessels of your body.

Let’s continue looking at some more examples.

Next, we have fat cells, also called adipocytes. These cells are relatively large in comparison to the other cells of your body. And they typically have a round, globular shape. Under a microscope, fat cells look a lot like soap bubbles. This is because they’re mostly filled with a huge vacuole, which stores fat. Depending on how much fat needs to be stored, these already large cells can quadruple in size. Compared to other cells, fat cells possess very little cytoplasm. Their primary function is to store excess energy in the form of fat.

Next, we have a type of epithelial cell called a squamous cell. Compared to the other cells of your body, they’ve got a small-to-average size. But squamous cells are specifically characterized by their flat, irregular shape. Because of their flattened shape, these cells also possess a flattened nucleus. And you can find them stacked in layers, lining and protecting many of the surfaces inside and outside of your body, including the outer layer of your skin and the inside of your mouth.

This same type of cell can be found in a single layer in other parts of your body, where instead of providing protection, they allow materials to pass through easily. Specifically, in your lungs and in your capillaries, or the very smallest blood vessels, their flat shape makes it easy for oxygen and carbon dioxide to move into and out of the bloodstream.

Next, let’s look at another type of epithelial cell.

Epithelial cells serve the function of lining certain parts of our body. And ciliated cells are a specialized type of epithelial cell. These cells are average size and columnar or oblong in shape. Their characterizing subcellular structure are the cilia or hair-like extensions of the cell membrane. These cilia are found on one surface of the cell, and they’re able to move in a wave-like motion. Ciliated cells are found lining the airways in your lungs and in your nasal passages, where they’re responsible for moving mucus around. They’re also found in the fallopian tubes, where they’re responsible for moving the egg cell from the ovary to the uterus.

Next, we’ll take a look at muscle cells, specifically skeletal muscle cells. These cells can be up to a few centimeters long. They’re thin fibers that are cylindrical in shape. Muscle cells come in three types: skeletal muscle, smooth muscle, and cardiac muscle. But what they all have in common is that their primary function is movement. In order to be able to contract and cause movement, these cells are packed with special proteins. They also have more than the average number of mitochondria, which provides them with the cellular energy they need to produce movement. Also, because of their length, skeletal muscle cells are multinucleated, which means that each cell has more than one nucleus inside.

Nerve cells are cells that are specialized for the purpose of transmitting signals from place to place. These cells are responsible for processing our thoughts, controlling our movement, and helping us to sense the world around us. They can be very long, up to a meter in length.

Nerve cells, also called neurons, have many different subcellular structures, including dendrites which receive signals from other cells, the axon which transmits the signal, the axon terminal which delivers the signal, and the myelin sheath, which acts in a similar fashion to electrical insulation, which serves the function of speeding up the transmission along the axon.

Remember, these cells can be quite long. The diagram shows a typical motor neuron or a neuron that controls movement. But the shapes of nerve cells tend to vary pretty widely. Depending on their specific function, they may possess dendrites or not. They may possess axons or not. And they may be myelinated or not.

The last two specialized cells that we’ll take a closer look at are our reproductive cells. The male human reproductive cell is called a sperm, and the female reproductive cell is called an egg cell or an ovum. Interestingly, the sperm cell is the smallest cell in the human body, and the egg cell is the largest. This smaller sperm cell is drawn to give us an idea of the relative size of these cells. And here we have a larger, more detailed diagram that allows us to see some of the subcellular structures.

The sperm cell consists of a streamlined head and a long motile or moving tail. Within the head of the sperm, we find the acrosome, which is a flattened sac that contains enzymes that help the sperm to penetrate the egg cell. We also find the nucleus, which is haploid, meaning that it contains half the normal number of chromosomes. At the base of the tail, we find several mitochondria arranged in a spiral shape. These carry out cellular respiration that provide the ATP, or cellular energy, that allows the tail to move. And finally, we have the tail, also called a flagellum. The movement of the tail propels the sperm towards the egg cell in a motion not unlike swimming.

The primary function of the sperm cell is to deliver the father’s genetic material to the egg. When an egg cell and a sperm cell fuse, it’s called fertilization.

In contrast, the egg cell is large and round. It also has a protective coating that serves the purpose of helping to ensure that only one sperm fertilizes the egg. Like the sperm cell, the egg cell is haploid, which means that it contains half the normal number of chromosomes. In this way, when the sperm cell and the egg cell fuse, the cell has the normal number of chromosomes needed for reproduction.

The cytoplasm of the egg cell also contains a high concentration of nutrients, which support the development of the early embryo after fertilization. We also already mentioned the outer layer which hardens after the egg cell is fertilized. This is meant to ensure that only one sperm cell penetrates the egg. The purpose of the egg cell is to facilitate fertilization by allowing one sperm to enter and by providing half of the genetic material needed to create an offspring. And since the sperm cell is basically just responsible for delivering DNA, the egg cell is also responsible for possessing all of the subcellular structures necessary for a fertilized egg cell to begin to develop into what will eventually become an offspring.

The structure of a cell is always related to its function. And in this video, we’ve looked at eight different examples. So let’s wrap up now by taking a moment to review what we’ve learned. In this video, we learned that the form or structure of a cell is directly related to its function or its job. We learned about cells specialized for the transport and storage of materials, two different types of epithelial cells, cells specialized for movement and communication, and our haploid reproductive cells.

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