Croft - Applying Basic Anatomy For Yoga Instructors and Everyone In Between

Introduction In my previous book titled Basic Anatomy For Yoga Instructors and Everyone In Between we discuss the basics of the human body. We covered things like bony landmarks, basic muscle actions, the effect of aging on bones and more. If you need to start at the very beginning, I hope you wil start with the first book then move onto this one. We will dive into some more specific aspects of the human body. We wil learn how muscles are structured and how they contract, how bones remodel and how reflexes work. We cover the origins, insertions, and actions of many muscles.

The nervous system and stress response are covered more in depth in this book than in the previous one. We also cover planes of motion and I share some of my common findings for muscle imbalances. Either book can stand alone, however, some information is built upon the knowledge gained in the first one. Copyright Alecia Croft 2020 1 | P a g e Table of Contents 2 | P a g e 3 | P a g e The whole System Before we begin our journey and dive deeper into some structures of the body, I want to acknowledge a few ways that everything is connected. How we live our lives plays a role in how we feel, how we appear and usually our overall happiness in general. Genetics, posture, eating, hydration, and our habits are just some of the components that play a role in who we are as individuals.

This also applies on a more intricate level, how much water we intake in a day impacts the hydration level of our body and its tissues. Whether we realize it or not, what we are nourishing our bodies with affects our energy level and more. When we make these types of decisions, we are impacting our entire body. Genetics also impact us, more than I think most of us realize. Look at how your parents walk. Now, look in the mirror or at your children.

It is amazing. Notice how you move throughout the day, see if you can relate how your tissues are impacted by this. 4 | P a g e Bones Our bones have different layers. We utilize these layers and different shapes and sizes of bones to our advantage as human beings. We are going to discuss the different layers of long bones here as they are a good example for bone structure. The diaphysis is the long portion, which is composed mainly of compact bone which surrounds a hollow center known as the medullary cavity.

Some spongy bone lines the medullary cavity. The epiphysis is found on the ends of the bone and consist of spongy bone primarily which are coated externally in compact bone. 5 | P a g e The growth plates, also known as the epiphysealplates, are located on each end between the diaphysis and epiphysis. Once a bone is full grown in length these plates become ossified and then are referred to as epiphyseal lines. The medullary cavity is fil ed with marrow. Marrow can also be found in the cavities of spongy bones.

Red bone marrow produces blood cells. Yellow marrow primarily stores fat cells. Bones are formed completely of red bone marrow before birth and start to change to a combination of yellow and red marrow just before birth. Eventual y in the limbs all the red marrow in long bones is replaced by yellow marrow. Other areas contain both red and yellow marrow. 6 | P a g e The inner surface of the bone cavities are lined with vascular connective tissue called endosteum.

The periosteum covers the outer layer of the bone and is comprised of a connective tissue membrane. Tendons and ligaments connect to the periosteum. 7 | P a g e Bone remodeling happens when new bone replaces old bone. The old bone is removed, and new bone is formed in its place. Over a length of ten years, in a full gown person, the entire skeleton is replaced through a specific process called a basic multi-cellular unit or BCU. Osteoclasts and osteoblasts that are assembled into BCU last about six months as they travel across or though the bones surface.

When bone remodeling occurs, old bone is removed by osteoclasts then new bone is formed in its place by osteoblasts. During this process woven bone is converted into lamellar bone. Depending on the type of bone tissue and shape of the bone the specific sites will vary with regard to where the osteoclasts remove bone and osteoblasts form bone. 8 | P a g e Muscles There are different layers of a muscle, just as there are different layers of bones. Each muscle cell is known as a muscle fiber. There are many layers that work together which help the muscle fibers function properly.

There are several layers of epimysium, which is an intricate layer of connective tissue. Deeper in the muscle it works to help nerves and blood flow to each muscle fiber while separating the individual muscle fibers that lie inside the fascicle. Epimysium eventually combines with muscular fascia, the outer 9 | P a g e layers help to keep organs, tissues and muscles separated from each other. Each muscle is subdivided into numerous bundles of muscle fibers by the perimysium. These visible bundles are known as fascicles. Each fascicle is supplied with nerves and blood vessels which passthrough the lose connective tissues of the perimysium. Motor neurons are responsible for making skeletal muscles contract. Beginning in the central nervous system motor neurons continue through nerves into skeletal muscles.

Each muscle is typically supplied by several motor neurons, which control multiple muscle fibers. Each branch of the motor neuron is responsible for a different muscle fiber. Neuromuscular junctions, or synapses, are where the axon and the muscle fibers meet. 10 | P a g e Muscle contractions contain an electrical component and a mechanical component. The electrical components consist of sarcolemma, the membrane of the muscle, composed of plasma. The sarcolemma have inward tube-like folds called Transverse tubules or T tubules that help each muscle fiber contract in unity.

The switch for muscle contraction lies in the sarcoplasmicreticulum which in skeletal muscle is composed of smooth endoplasmic reticulum that is highly specialized. The mechanical components consist of bundles of muscle cells known as myofibrils. These long fibers resemble thread and run the length of the muscle fiber. The myofibrils contain protein filaments, which interact during the muscle contraction to shorten the muscle fibers. Actin and myosin are different types of myofilaments. Actin is a thin myofilament, while myosin is a thick myofilament. Combined into orderly units they are called sarcomeres, which is the structural and functional unit of skeletal muscles.

Muscle contraction is the primary function of skeletal muscles. The parallel alignment of myofilaments in a sarcomere are what allow muscle contractions to be possible.