ISSA SN Chapter 12: Anatomy of an Athlete: Cells, Tissues, and Systems
ISSA SN Chapter 12: Anatomy of an Athlete: Cells, Tissues, and Systems

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    Chapter Goals:

    • Describe and define the main terms that relate to human anatomy.
    • Know about the structure of cells.
    • Find and understand the main systems we have in our bodies.
    • Describe the varying muscle fiber types and the types of muscle contractions that we can go through.


    Anatomy is simply defined as the structures of the body. 

    Physiology is simply defined as the function of the body.

    This chapter is going to go over these two concepts as they relate best to sports science.

    Cells, Cells, Cells

    Our bodies are a biological phenomenon due to the many interdependent systems working together to maintain life. We have systems like the circulatory system which is needed to give the muscular system nourishment and also carry away the waste products we produce. The system for digestion is made up of many organs that work to break down things in the body. And we have many more systems that we will discuss throughout, and they are all made up of cells. Cells designed with different goals and processes in mind.

    The Cell – Fundamental Unit of Life

    Like every molecule has its own building blocks, our tissues and our structures do too. These are cells. The small units that give us life. We estimate that there are around 100 trillion cells with many different forms and functions spread throughout the average human body. 

    One crazy characteristic of cells is that they are able to reproduce themselves. They can actually only come from cells that existed before. The process starts with one cell in the form of the female’s egg, and the other in the form of the male sperm cell. These merge into a zygote, and then through multiplication and ordering we get to the trillions of cells we have in our body. 

    This process continues automatically, and all we really need to do is provide nutrients through our food.

    Cellular Components:

    The plasma membrane is like an inflated balloon. It is the outer membrane of the cell. This complex structure is mainly made of proteins and a phospholipid bilayer. The bilayer forms a double walled balloon structure where proteins are embedded within. Proteins provide structure for the membrane, they form channels that allow passage for certain things, they acts as receptors for important information, they may function as transports for some materials, and they give a marker for identification of the cells. These are essentially the functions of the plasma membrane.

    The Nucleus was discovered over 150 years ago. It is placed in the center of the cell and it has its own membrane. This is the housing center for the DNA of the cell. Those strands of DNA together make up our chromosomes, for which we have 46 in total. These chromosomes contain our genetic information that decides how we look and how the body performs. We could call the nucleus the control center of the cell. The liquid between the nuclear membrane and the plasma membrane is known as the cytoplasm. 

    The ribosomes are an important organelle for cells. They play a role in synthesizing the proteins and cell parts we need. These ribosomes are going to be extremely tiny. They consist of protein and RNA. They are the most numerous organelles found in cells. We can find them spread throughout the cytoplasm or attached to the endoplasmic reticulum. 

    The endoplasmic reticulum is the next organelle to mention. This is an organelle that makes a network of canals in the cytoplasm and is involved in the transport of materials. The endoplasmic reticulum has two forms, the rough and the smooth forms. The smooth endoplasmic reticulum appears as smooth due to the absence of the ribosomes on the outside. And the opposite is true for the rough ER. We also have evidence of some lipid and cholesterol metabolism occurring in liver cells’ endoplasmic reticulums. 

    The Golgi apparatus is next. This is made up of stacks of oblong sacs that are embedded in the cytoplasm close to the nucleus. It actively modifies and transports some proteins. Some carbohydrate biomolecules have been seen to be produced through this organelle also. 

    The lysosomes are some structures like sacs that have their size and shape changed depending on what activity they will do. They begin as very small, and then when they are active we see them increase their size significantly. They contain many types of enzymes within. These are used to carry out varying chemical reactions and breaking down the components when the need be. These broken down components can then be used to synthesize new molecules by the cells. So, they play a very vital role to the formation of new components. 

    The mitochondria are the cells near the nucleus. They are the most discussed organelle of them all. They are often known as the powerhouse of the cell due to their role being the production of energy for everything we do. Different cells we have varying amounts of these important energy producing organelles. This is all based on if the cell needs to produce energy.


    Tissues would be the fundamental units of function and for structure, if the cells are the fundamental units for life. We define tissues as the aggregation of cells that are bound together and work to perform one common function of some kind. Like our adrenal cortex for example. We see this working together to produce several related hormones. These are example of tissue. 

    Epithelial Tissues

    These are tissues we see throughout our body in the forms of skin, the inner cavities of the body, or the makeup of some of the glands in the body. these tissues work to protect the cells that are underneath them from bacteria, chemicals, and drying. The epithelial tissues have four different groups that they can fall under.

    Squamous epithelium is the tissue that is made up of mostly flat cells. It is located in our mouths, the esophagus, and the blood or lymphatic cells. Substances are easily able to diffuse through these. 

    Cuboidal epithelium is the second type. These tissues are those that are shaped like cubes and found throughout the tubules of the kidney. 

    Columnar Epithelium are the tissues that will look like pillars or columns. They are going to be found in the digestive tract and the respiratory tract mostly. They are used for either secretion or absorption. Some of them even contain some small hair cells known as cilia in order to increase the surface area of these tissues. 

    Glandular Epithelium are the fourth form of these tissues and they are specialized for the secretion of mucous and hormones. The examples would be the thymus glands and the salivary glands. 

    Connective Tissues

    These tissues throughout the body are used for connection and for support. They join things together and they are made up of cells that are embedded in a nonliving matrix. The matrix’s nature determines the function of the cells, instead of the cells alone. 

    Even blood is going to be considered a connective tissue due to the containing of a fluid matrix and the cells being technically suspended within. 

    Connective tissues are made up of many constituents.

    There are three main fibers that are kept in the connective tissues.

    Collagen fibers are the really strong fibers that are going to form the fibrous parts of skin, tendons, ligaments, and teeth. They are made up of five main amino acids. collagen is going to give the connective tissue the versatility it needs to interconnect with the other molecules. These fibers are found in bundles and this gives them their exceptional strength. 

    Reticular fibers are the second type of fibers. These are very delicate fibers that provide support for the connective tissues that are found in the networks like the capillaries and the nerve fibers. 

    The elastic fibers are simply going to be the ones that are extendible and elastic in nature. 

    The main connective tissues are going to be cartilage, bones, tendons, and the ligaments. 

    Cartilage forms the bone tissue’s foundation. It is found at the ends of the bones and in the spinal disks. Matured cartilage does now have any nerves or blood vessels in it. We actually have three forms of cartilage in the body. the elastic cartilage in the ear and the Eustachian tubes, the tough fibrous cartilage that is between bones and the spinal disks, and hard hyaline cartilage that is at the ends of the bone also, and the nose, larynx, and trachea. 

    Bones are what forms our skeleton. This skeleton and the bones in it will act to support and protect the body. the bones resemble and differ from the cartilage. Like the cartilage, though, the bone is made up more of intracellular substances than of cells. These substances are hardened as opposed to the gel like appearance of cartilage. Collagen fibers are also inside the calcified matrix of bones. Inside this calcified matrix, the cells are quite alive. There are many blood vessels that are constantly delivering the food and oxygen for the cells. 

    The tendons and ligaments are grouped together. These are going to be very strong structures that are quite flexible also. They are our strongest tissues in the body actually. Their intracellular matrix is made up of collagen and reticular fibers that come from surrounding tendons. Tendons are thick and their main goal is to connect the muscles and the bones along with many other structures. Ligaments will join the bone to other bone, like in joints. 

    Muscle Tissues

    Muscle is about 43 percent of the total of a man’s weight and 34 percent for women. There are a total of around 620 muscles that all work together to support the skeletal system and create the motions we do every day. There are around 30 muscles we use to help with food and the digestive system, blood circulation, and the operation of some organs. For this book, the muscles will be primarily talked about as the main source of operation, energy expenditure, waste generation, and substantial nutrient needs.

    Muscle may contract voluntarily or involuntarily. The voluntary muscle and their movements will come from the somatic nervous system, and this is all of our skeletal muscles. The involuntary muscle tissues are controlled by the autonomic nervous system, and these cannot be controlled by us. 

    We have two forms of muscle tissue that we see when looking under a microscope. These are striated muscles and smooth muscles. We can divide these into three categories. 

    Cardiac muscle tissue is striated and involuntary. It composes the heart muscle. It works to contract the heart, and that then pumps the blood through the body. 

    Smooth Muscle Tissue is smooth, and it is involuntary. It is found in the areas such as the tubular viscera of the digestive, respiratory, and genitourinary tracts. These will function to move substance through their respective systems. They contract slower than other striated muscles will and thus they do not fatigue quickly. 

    Skeletal muscle is found attached to bones, the eyes, and the upper third of the throat. The skeletal tissue will function to move bones and our eyes, or the food we swallow in the first parts of digestion. These muscles have very long cells with many nuclei. They rarely ever contract with one muscle alone. Instead we see sets of muscles contract in order to produce movement. the spine and the brain exercise control over these complex movement patterns through the use of nerve fibers. 

    Each cell does not have its own line from the CNS. Instead they get them to whole groups of these muscles at once and contract together. 

    The special sense organs in our muscles that help with control are called muscle spindles. They essentially measure the amount of strain in the muscle and preset tension. 

    The skeletal muscles will contract much more rapidly as responses to the CNS system. 

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    The Mechanics of Muscular Contraction

    The external view of the skeletal muscles make them appear as grainy due to the makeup of extremely small fibers. They are divided into bands and look like a stack of coins in a pile. Each fiber has its own sarcolemma, which is a small plasma membrane. Myofibrils are the tiny fibrils names. They number from some hundred, to several thousand. The sarcoplasm of the muscle cells has many nuclei within it. It also has many mitochondria. 

    The fibrils are made out of two different proteins. These are actin and myosin. They work together to contract the muscles.

    Fast-Twitch and Slow-Twitch Muscle Fibers

    There are these two forms of muscle fibers, fast and slow twitch. 

    Slow twitch fibers are the ones that produce power for lower intensity exercise, they have repetitive contractions, and they are mostly used for our endurance activities. The athletes in these long distance events and sports are more likely to have a high percentage of slow twitch fibers. 

    The fast twitch fibers are the ones that we recruit selectively for heavy workloads where we need maximum strength and power. These are seen more so in athletes that are in weightlifting and sprinting and similar sports. 

    Muscular Hypertrophy

    This is simply defined as an increase in the size of the muscle fibers. The main mechanism at work is going to be an increase in the number of myofibrils. 

    Hyperplasia is the process of increasing the number of cells that are in the muscles. This is less often but occurs when fibers split.


    All of the tissues in our body work together to form the functional units that we call systems. The body is essentially one whole system that is made up of subsystems. These subsystems are what we will call systems, even if the body is the real ‘system’. 

    Skeletal System

    This is made up of all of the bones in our body and the joints they are attached to or through. The main tissues here are going to be bones, cartilage, ligaments, and hematopoietic tissue.

    Skeletal Muscle System

    This is made up of the muscle tissues of our body that are responsible for movement and controlled by the somatic system. The muscles are limited to the storage of proteins in the form of amino acids. the use of these is not wanted for athletes due to the poor effects on the muscles.

    Nervous System

    This system is made up of all of our neurons, neuroglia, and the neurosecretory cells. They provide memory and integrate our bodily functions, control, and our communication.

    Respiratory System

    This is made up of the organs of the nose, lungs, bronchi, trachea, larynx, and pharynx. They all function to connect the gaseous environment with our cells of the human body. 

    Cardiovascular (Circulatory) System

    This is made up of the heart, the veins, the arteries, and the lymphatic system. This is in charge of circulation which is the movement of fluid, lymph, and blood through the body to carry important things around. 

    Digestive system

    The five organs hear are the mouth, pharynx, esophagus, stomach, and the intestine, both small and large. These work together to control the intake and absorption of nutrients into the body so we can live and thrive.

    Urinary System

    This consists of the kidneys, the ureters, the bladder, and the urethra. They function to flush the waste from the body in the form of urine. It is a way to keep homeostasis of the body, which is the tendency to maintain equilibrium. 

    Reproductive System

    This system has the organs that function to make sperm in males and eggs that are fertile in the females. 

    Endocrine System

    This is the system that is made up of many organs all with their own hormones to produce. They function together to provide the body with its needed hormones for its very many functions. 

    ISSA SN Chapter 12: Anatomy of an Athlete: Cells, Tissues, and Systems 1
    ISSA SN Chapter 12: Anatomy of an Athlete: Cells, Tissues, and Systems 2
    ISSA SN Chapter 12: Anatomy of an Athlete: Cells, Tissues, and Systems 3

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