This is a network of a large number of neurons that is designed modulate, generate, and transmit information with the different parts of the body thus facilitating important body functions. It is basically the electrical wiring of the body. Structurally the nervous system is divided into central nervous system (the brain, spinal cord and nerves) and peripheral nervous system made up of sensory neurons, ganglia and nerves. Functionally the nervous system is divided into somatic and autonomic component. The CNS integrates all the sensory and motor information of the body. The nervous system has two components the gray and white matter. Gray matter contains lots of neuron bodies and white is made of axons. The peripheral nervous system has receptors that detects changes in the environment and send information to the CNS where it is processed and a feedback relayed to the PNS through peripheral nerves. The autonomic nervous system controls functions of the body without our conscious thought such as heart rate and perspiration Nerves are bundles of fibers cylindrical in shape originating from the brain through the spinal cord and then distributed throughout the body. Neurons communicate with other cells through neurons which triggers the release of neurotransmitters at the synapse. A synapse then relays the message to the cells. Sensory neurons are sensitive to physical stimuli such as touch, sound and light and give the CNS information about the environment. Motor neurons transmit information that stimulates muscles or glands. Gliad cells are specialized cell that nourish protect and support nerve cells.
Circulatory System
This is the bodies transport system. It is made up of the heart, blood, and the blood vessels. The heart’s primary role Is to pump blood throughout the body. It is a muscle that is fist sized. It has a fibrous covering called the pericardium that wraps around the heart. This holds the heart in place aids it in beating faster. The walls are made up of cardiac muscle. The heart has four chambers. The two top chambers are the right and left atria while the lower two are the right and left ventricles. Left atrium receives blood from the lung and the right atrium receives blood from the various body parts. The right ventricle pumps blood to the lungs while the left ventricle pumps blood to the rest of the body. Ventricles are thicker than the atria since they need to put more effort to pump blood quickly. Blood vessels carry blood. The heart has valves that prevent the blood from flowing backwards. Ventricles carry blood towards the heart while the arteries carry blood away from the heart to the rest of the body. Capillaries are microscopic blood vessels that connect the veins and arteries together. Since the capillaries are found deep into the muscles and organs, this is where oxygen and other nutrients find their way into the needy tissues and waste products from metabolism from the tissues is released into the blood stream. There are two types of circulation involved. The systemic circulation that provides organs with oxygen and nutrients and the pulmonary circulation where fresh oxygen is introduced into the blood stream and carbon dioxide released (Humphrey, M.et al, 2003).
Muscular System
Muscle tissues are of three types; the visceral, cardiac and skeletal. Visceral muscles are found in organs such as blood vessels, intestines and the stomach. They are the weakest of all the muscles and they function by moving substances through the organ such as food in the digestive tract. These muscles are involuntary and cannot be controlled by a conscious mind. Cardiac muscles are only found in the heart. It is responsible for delivering blood throughout the body. This muscle cannot be controlled by the brain too. Hormones and signals from the brain control the rate of their contraction. It is a self-contracting muscle hence intrinsically controlled. These cell muscles are branched in an X and Y manner and tightly connected using intercalated disk which enables it to withstand the strain of pumping blood for a life time. Skeletal muscles are voluntary muscles thus can be controlled consciously. They contract to move parts of the bone near the bone. Most of these muscles are interconnected to two bones at a joint. They are formed due to lots of lumping of many small progenitor cells to form long strait multinucleated fibers. Much attachment to bones is through tendons. They are tough and have collagen fibers that attach muscles to bones. To achieve movement, skeletal muscles rarely work independently thus they work in groups to achieve motion. An agonist mover is a muscle that produces any kind of movement and it always pairs with the antagonistic muscle. We also have synergist muscle which help in stabilization of movement and help stabilize a movement or prevent extraneous motions ("Muscular System - Muscles of the Human Body", 2021).
Skeletal Muscle
Skeletal muscles are hard and their function depends on the hardness of the bone. The long bone is made up of two parts diaphysis and epiphysis. The diaphysis presents as a shaft that runs from the proximal to the distal ends. The medullary is a hollow region in the diaphysis that is packed with yellow marrow. The bone of the diaphysis is hard and compact. Epiphysis is found at the ends of the bone and is usually spongy. The spaces inside this spongy bone are filled with the red marrow. Epiphysis meets the diaphysis at epiphyseal plate also knows as the growth plate. During adulthood this plate is replaced by osseous tissue. The medullary cavity has endosteum which facilitates bone repair, growth and remodeling. The outer surface of the bone is covered with periostem which houses blood vessels, lymphatic vessels and nerves which service the compact bone. Epiphyses have articular cartilage that aids in reducing friction and acts as a shock absorber. Flat bones such as cranium bones have diploe lined on both sides by a layer of compact bone which work together so as to protect the internal organs in case of fractures. Bones have few cells entrenched in collagen fibers which provide an attachment surface for inorganic salts to collect which then form hydroxyapatite crystals which are responsible for their hardening. Collagen fibers prevent brittleness of the bone. Cells found in bones include osteoblasts, osteocytes, osteogenic cells and osteoclasts. Osteoblasts are found in growing portions of the bone and it forms new bone. Osteoblasts are involved in the synthesis and secretion of collagen matrix and calcium salts. Osteoclasts are involved in bone reabsorption for old and damaged bone (Bone Structure", 2021).
Respiratory System
Respiratory tract is divided into the upper and the lower respiratory tract. The upper respiratory tract comprises of paranasal sinuses, pharynx, nasal cavity and a portion of the larynx above the vocal cords. The lower respiratory tract include larynx below the vocal chords, trachea, bronchi, bronchioles and the lungs. Lungs may be singled out as a separate entity. It contains respiratory bronchioles, alveolar sacks, alveolar ducts, and alveoli. The nasal cavity opens on the face with two nares. The anterior portion of the nasal cavity and the nares contains sebaceous glands and hair follicles which prevent harmful substances from gaining entry. The nasal concha in the nasal cavity disrupts laminar air flow facilitating air humidiation and warming to body temperatures. The roof of the nasal cavity has olfactory epithelium with sensory cells necessary for the sense of smell. The paranasal sinuses continue the warming and humidification of air. They also have mucus membrane that traps dust, harmful particles and bacteria. Next the air enters the pharynx which is funnel shaped and muscular. It is made up of nasopharynx, laryngopharynx, and oropharynx. The pharynx swings up during swallowing to prevent food from entering the nasal cavity. The larynx follows which is hollow with cartilaginous membranes. It conducts air and houses vocal cords that are used in voice production. The trachea then branches to left and right bronchi which further divide into bronchioles and lead into alveoli where gaseous exchange begins. From here it enters the lungs. The lung contains principle bronchus, pulmonary artery, two pulmonary veins and bronchial vessels.
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References
Bone Structure. (2021). Retrieved 23 January 2021, from https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Book%3A_Anatomy_and_Physiology_(OpenStax)/Unit_2%3A_Support_and_Movement/06%3A_Bone_Tissue_and_the_Skeletal_System/6.03%3A_Bone_Structure
Humphrey, J., & McCulloch, A. (2003). The Cardiovascular System — Anatomy, Physiology and Cell Biology. Biomechanics of Soft Tissue in Cardiovascular Systems, 1-14. doi: 10.1007/978-3-7091-2736-0_1
Muscular System - Muscles of the Human Body. (2021). Retrieved 23 January 2021, from https://www.innerbody.com/image/musfov.html
