Note: The contents of this blog are for informational purposes only and should not be construed as medical advice or substitute for professional care. For medical emergencies, dial 911!
I am a Licensed Practical Nurse with five years' experience in this profession. I believe it is essential to go back to the basics in all things in order to really understand them. I am fascinated by how our bodies work and I hope I can get my readers to share my fascination. I hope we all learn new things and marvel again at the things we already know. This feature -- which includes a closing section on how disease affects the topic in question -- will run on The Cancer Blog on Wednesdays, and The Cardio Blog and The Diabetes Blog on Thursdays. [The contents in this post are for informational purposes only and should not be construed as medical advice or substitute for professional medical care.]
We looked at the cell in a series of six articles and now we are moving into the fascinating world of tissues. A tissue is a group of cells with similar structure and function. The tissue then contributes to the functioning of the organs in which it is found. Epithelial tissue exists at the body surface where it lines the skin and various organs such as the mouth, nose and other body cavities. It is also found at the lining of the respiratory, reproductive and urinary tracts. All blood vessels are also lined with epithelial tissue. Epithelial tissue is divided into different types.
The first type of epithelial tissue is the covering and lining epithelium. It forms the epidermis of the skin and the outer covering of some internal organs as well as the inner lining of blood vessels, ducts and body cavities. It is arranged by layers and cell shapes. The layers are: simple epithelium, stratified epithelium and pseudostratified columnar epithelium. The cell shapes are: Squamous, cuboidal, columnar and transitional.
Simple squamous epithelium: It consists of a single layer of flat cells that resembles a tiled floor. It is located in the lining of the blood vessels, lining of body cavities and part of the kidney tubules. Its functions are protection and absorption.
Simple cuboidal epithelium: The cuboidal shape of the cells in this tissue is obvious when the tissue is sectioned and viewed from the side. It is located in the secretory portion and ducts of some glands and part of the kidney tubules. Its functions are secretion and protection.
I am a Licensed Practical Nurse with five years' experience in this profession. I believe it is essential to go back to the basics in all things in order to really understand them. I am fascinated by how our bodies work and I hope I can get my readers to share my fascination. I hope we all learn new things and marvel again at the things we already know. This feature -- which includes a closing section on how disease affects the topic in question -- will run on The Cancer Blog on Wednesdays, and The Cardio Blog and The Diabetes Blog on Thursdays. [The contents in this post are for informational purposes only and should not be construed as medical advice or substitute for professional medical care.]
We start with the cell, because so much of what happens to us when we get sick, and how we get healthy again, can be explained by what happens on a cellular level. The cell is extremely complex and I will only touch on the basics in these posts, but at least we can have a rudimentary understanding.
We have discussed cell membranes (May 24), as well as cell organelles (May 31). On June 7, we discussed the cellular transport mechanisms and on June 14 the cell nucleus. On June 21 we discussed cell division and in this last post on the cell, we are taking a short look at protein synthesis.
Although cells synthesize many chemicals to maintain homeostasis, they are mainly devoted to synthesizing large numbers of proteins. Proteins are used as enzymes and as structural materials in the cells. Many proteins are retained in the cell for intracellular use. Some proteins are used to assemble cellular structures such as the plasma membrane, the cytoskeleton and other organelles. There are many specialized human proteins that are exported and function in cellular activities. For example, protein makes up the hormone insulin, the ligaments and tendons of joints, the hair, skin, and nails of the body.
I am a Licensed Practical Nurse with five years' experience in this profession. I believe it is essential to go back to the basics in all things in order to really understand them. I am fascinated by how our bodies work and I hope I can get my readers to share my fascination. I hope we all learn new things and marvel again at the things we already know. This feature -- which includes a closing section on how disease affects the topic in question -- will run on The Cancer Blog on Wednesdays, and The Cardio Blog and The Diabetes Blog on Thursdays. [The contents in this post are for informational purposes only and should not be construed as medical advice or substitute for professional medical care.]
We start with the cell, because so much of what happens to us when we get sick, and how we get healthy again, can be explained by what happens on a cellular level. The cell is extremely complex and I will only touch on the basics in these posts, but at least we can have a rudimentary understanding.
We have discussed cell membranes (May 24), as well as cell organelles (May 31). On June 7, we discussed the cellular transport mechanisms and on June 14 the cell nucleus.As we near the end of this series on the cell, we get to one of the most interesting parts: cell division.
One of the features of a cell is it's ability to reproduce independently. In somatic cell division, a cell undergoes a nuclear division called mitosis. Reproductive cell division is the mechanism that produces gametes. This process consists of a two step division called meiosis.
In this post we will look at the process of mitosis. Each of us began life as one cell, a fertilized egg. Each of us now consists of billions of cells produced by the process of mitosis. In mitosis one cell with the diploid number of chromosomes (46, except in chromosomal abnormalities) divides into two identical daughter cells, each with the diploid number of chromosomes. Mitosis is a continuous process compromised of a series of events. This series of events are divided into different stages called: prophase, metaphase, anaphase, telophase and cytokinesis. Prior to these events interphase occurs, which is divided into 3 phases of its own.
I am a Licensed Practical Nurse with five years' experience in this profession. I believe it is essential to go back to the basics in all things in order to really understand them. I am fascinated by how our bodies work and I hope I can get my readers to share my fascination. I hope we all learn new things and marvel again at the things we already know. This feature -- which includes a closing section on how disease affects the topic in question -- will run on The Cancer Blog on Wednesdays, and The Cardio Blog and The Diabetes Blog on Thursdays. [The contents in this post are for informational purposes only and should not be construed as medical advice or substitute for professional medical care.]
We start with the cell, because so much of what happens to us when we get sick, and how we get healthy again, can be explained by what happens on a cellular level. The cell is extremely complex and I will only touch on the basics in these posts, but at least we can have a rudimentary understanding.
We have discussed cell membranes (May 24), as well as cell organelles (May 31). On June 7, we discussed the cellular transport mechanisms. Today we will look briefly at the cell nucleus. As with the other parts of the cell, this can be a short discussion or a series of articles in and of themselves. I have decided to stay very basic and not discuss each component separately.
With the exception of mature red blood cells, human cells have a nucleus and some, like skeletal muscle cells, have more than one. The nucleus is composed of three main parts, the nuclear envelope, the nucleolus and the chromatin.
The nucleus is separated from the cytoplasm by a double membrane (nuclear envelope)that have lipid bilayers like the plasma membrane. The outer membrane of the nuclear envelope is continuous with the rough endoplasmic reticulum (ER). It controls the movement of substances between the nucleus and the cytoplasm through nuclear pores -- channels that perforate the nuclear envelope. Small molecules can diffuse through the nuclear pores, but larger molecules, like ribonucleic acid (RNA), need to use active transport facilitated by carrier proteins. The other structural element of the nucleus is the cellular lamina, a mesh-work that adds support, much like the cytoskeleton supports the cell as a whole.
I am a Licensed Practical Nurse with five years' experience in this profession. I believe it is essential to go back to the basics in all things in order to really understand them. I am fascinated by how our bodies work and I hope I can get my readers to share my fascination. I hope we all learn new things and marvel again at the things we already know. This feature -- which includes a closing section on how disease affects the topic in question -- will run on The Cancer Blog on Wednesdays, and The Cardio Blog and The Diabetes Blog on Thursdays. [The contents in this post are for informational purposes only and should not be construed as medical advice or substitute for professional medical care.]
We start with the cell, because so much of what happens to us when we get sick, and how we get healthy again, can be explained by what happens on a cellular level. The cell is extremely complex and I will only touch on the basics in these posts, but at least we can have a rudimentary understanding.
We have discussed cell membranes (May 24), as well as cell organelles (May 31). Before we look at the nucleus of the cell, I would like to do a short post on some of the mechanisms for molecular movement across the cell membrane. Transport across the cell membrane is important to understand, because a lot of the newer research seems to focus on this aspect.
Living cells constantly interact with the external environment, like tissue or blood. In order to do that, materials must move through the plasma membrane, taking in some substances and secreting or excreting others. There are several methods by which movements can occur: diffusion, osmosis, facilitated diffusion, active transport, filtration, endocytosis and exocytosis. We will look at each of these briefly.
I am a Licensed Practical Nurse with five years' experience in this profession. I believe it is essential to go back to the basics in all things in order to really understand them. I am fascinated by how our bodies work and I hope I can get my readers to share my fascination. I hope we all learn new things and marvel again at the things we already know. This feature -- which includes a closing section on how disease affects the topic in question -- will run on The Cancer Blog on Wednesdays, and The Cardio Blog and The Diabetes Blog on Thursdays. [The contents in this post are for informational purposes only and should not be construed as medical advice or substitute for professional medical care.]
We start with the cell, because so much of what happens to us when we get sick, and how we get healthy again, can be explained by what happens on a cellular level. The cell is extremely complex and I will only touch on the basics in these posts, but at least we can have a rudimentary understanding.
Structure of cells
A cell has three basic parts:
1) Plasma membrane: A membrane lies at the border of cells and consists of lipids and proteins. See my post of 23 May on the cell membrane
2) Cytoplasm: All the cellular contents between the plasma membrane and the nucleus and can be further divided into the Cytosol and Organelles. We will discuss the organelles in today's post.
3) Nucleus: Technically an organelle, but usually considered separately because of its numerous and diverse functions.
Organelles
Organelles are specialized structures that evolved to perform specific functions. We could probably discuss each organelle in a separate post, because each one has it's own characteristic shape and function. i decided to keep this very basic and just list the different organelles, what they look like and what their basic function is. We will also just look at the "famous" organelles. There are other organelles, but the ones we discuss will give us a good understanding of what goes on inside the cell.
I am a Licensed Practical Nurse with five years' experience in this profession. I believe it is essential to go back to the basics in all things in order to really understand them. I am fascinated by how our bodies work and I hope I can get my readers to share my fascination. I hope we all learn new things and marvel again at the things we already know. This feature -- which includes a closing section on how disease affects the topic in question -- will run on The Cancer Blog on Wednesdays, and The Cardio Blog and The Diabetes Blog on Thursdays. [The contents in this post are for informational purposes only and should not be construed as medical advice or substitute for professional medical care.]
We start with the cell, because so much of what happens to us when we get sick, and how we get healthy again, can be explained by what happens on a cellular level. The cell is extremely complex and I will only touch on the basics in these posts, but at least we can have a rudimentary understanding.
Structure of cells
A cell has three basic parts:
1) Plasma membrane: This post will discuss the membrane in more detail.
2) Cytoplasm: All the cellular contents between the plasma membrane and the nucleus and can be further divided into the Cytosol and Organelles.
3) Nucleus: Technically an organelle, but usually considered separately because of its numerous and diverse functions.
Membrane
A membrane lies at the border of the cells. It consists of lipids and proteins.
Phospholipids (one of the three classes of membrane lipids) are formed into what is called a lipid bilayer. This occurs because it is amphiphilic (containing both hydrophobic and hydrophilic properties). The hydrocarbon tails of the molecule are hydrophobic (water repelling) and its polar head it hydrophilic (water loving). As the plasma membrane faces watery solutions on both sides, its phospholipids accommodate this by forming a phospholipid bilayer with the hydrophobic tails facing each other. Picture a row of heads facing the outside of the cell -- which contains water -- with the tails facing in and another layer of the heads facing the inside of the cell with the tails facing in.
The first type of epithelial tissue is the covering and lining epithelium. It forms the epidermis of the skin and the outer covering of some internal organs as well as the inner lining of blood vessels, ducts and body cavities. It is arranged by layers and cell shapes. The layers are: simple epithelium, stratified epithelium and pseudostratified columnar epithelium. The cell shapes are: Squamous, cuboidal, columnar and transitional. 
Although cells synthesize many chemicals to maintain homeostasis, they are mainly devoted to synthesizing large numbers of proteins. Proteins are used as enzymes and as structural materials in the cells. Many proteins are retained in the cell for intracellular use. Some proteins are used to assemble cellular structures such as the plasma membrane, the cytoskeleton and other organelles. There are many specialized human proteins that are exported and function in cellular activities. For example, protein makes up the hormone insulin, the ligaments and tendons of joints, the hair, skin, and nails of the body.
One of the features of a cell is it's ability to reproduce independently. In somatic cell division, a cell undergoes a nuclear division called mitosis. Reproductive cell division is the mechanism that produces gametes. This process consists of a two step division called meiosis. 
With the exception of mature red blood cells, human cells have a nucleus and some, like skeletal muscle cells, have more than one. The nucleus is composed of three main parts, the nuclear envelope, the nucleolus and the chromatin.
We have discussed cell membranes 
Organelles
We start with the cell, because so much of what happens to us when we get sick, and how we get healthy again, can be explained by what happens on a cellular level. The cell is extremely complex and I will only touch on the basics in these posts, but at least we can have a rudimentary understanding.
Phospholipids (one of the three classes of membrane lipids) are formed into what is called a lipid bilayer. This occurs because it is amphiphilic (containing both hydrophobic and hydrophilic properties). The hydrocarbon tails of the molecule are hydrophobic (water repelling) and its polar head it hydrophilic (water loving). As the plasma membrane faces watery solutions on both sides, its phospholipids accommodate this by forming a phospholipid bilayer with the hydrophobic tails facing each other. Picture a row of heads facing the outside of the cell -- which contains water -- with the tails facing in and another layer of the heads facing the inside of the cell with the tails facing in.
