human body systems

• SYSTEM OF ORGANS is a group of organs that work together to perform one or more functions in the body.
• The nervous system is responsible for receiving, processing, and responding to information from both inside and outside the body.
• Musculoskeletal system is the Mechanical support, posture and locomotion
• Urinary System is the removal of waste products from the body
• The muscular system consists of all the body muscles
• where you can find the smooth muscle?

  within the walls of blood vessels

  hollow organs ex. stomach and intestines
• Cardiac muscle cells form the heart muscle, also called the false
• skeletal muscle attaches to bones by tendons and allows movement at joints
• skeletal and cardiac muscle fibers are arranged in a repetitive fashion giving a striped appearance, hence are called striated muscle
• skeletal muscles can be controlled consciously and enable us to produce body movement
• smooth and cardiac muscle function is regulated by the autonomic nervous system and absolutely unconscious
• The cardiovascular system is comprised of the heart and the circulatory system of blood vessels.
• Blood enters the heart through the upper chambers of the left and right atria and exits via the left and right ventricles. Heart valves prevent the backflow of blood.
• The heart acts as a two-way pump. The right side of the heart pumps deoxygenated blood into the pulmonary circulation of the lungs, where the blood is reoxygenated again. While the left side of the heart simultaneously pumps oxygenated blood into the systemic circulation, distributing it to the peripheral tissues. The regular pumping, or heartbeat, is controlled by the conduction system of the heart.
• The circulatory system, also called the vascular system, consists of arteries, veins and capillaries. They all comprise a continuous network of vessels which act to carry blood around the body. Blood leaves the heart via arteries, these progressively reduce in size to continue as smaller arterial vessels called arterioles. Arterioles end in a web of even smaller vessels called capillaries. The exchange of gases and nutrients occurs through the capillary walls.
• Small veins, called venules, leave from capillaries and gradually increase their lumen on the way to the heart to end as veins. There is a certain histological difference between arteries and veins, but their main functional difference reflects the direction in which they conduct blood: the arteries convey blood from the heart to the periphery, whereas the veins convey blood from the periphery to the heart
• There are three separate circuits to the circulatory system.

  • The pulmonary circulation which carries blood between the heart and the lungs;
  • The coronary circulation which supplies blood to the muscle of the heart;
  • And the systemic circulation which carries blood to the rest of the body.

  Major arteries within the systemic circulatory system are the aorta and its branches, while the main representatives of the veins are the superior vena cava and inferior vena cava.
• The respiratory system consists of a series of organs; the nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and lungs (alveoli). The nasal cavity and pharynx are together called the upper respiratory system, while the remainder of the organs comprise the lower respiratory system.
• Nervous system controls how we interact with and respond to our environment, by controlling the function of the organs in our other body systems. The nervous system organs are the brain, spinal cord and sensory organs. These are connected by neurons, which act to transmit neural signals around the body. 
• The central nervous system definition is that it receives information from the body’s environment and generates instructions, thereby controlling all the activities of the human body. This two-way information flow into, and out of, the CNS is conveyed by the peripheral nervous system. 
• The CNS consists of the brain and spinal cord. The brain is placed within the neurocranium, and is formed from the cerebrum, cerebellum and brainstem (pons and medulla oblongata). The central parts of the CNS are occupied by spaces called ventricles filled with cerebrospinal fluid (CSF). The spinal cord is placed within the vertebral column. The spinal canal extends through the central part of the spinal cord. It is also filled with CSF and it communicates with the ventricles of the brain.
• The gray matter is where the instructions generate, while the white matter is the path through which the instructions travel toward the organs.
• The peripheral nervous system definition is that it conducts information from the CNS to the target tissues, and from the target tissues to the CNS. It consists of nerves and their ganglia. Nerves that carry information from peripheral sense organs (for example eye, tongue, nasal mucosa, ear, skin) to the CNS are called the ascending, afferent or sensory nerve fibers. Fibers that carry information from the CNS to the periphery (muscles and glands) are the descending, efferent, motor or secretory nerve fibers.
• Peripheral nerves emerge from the CNS. There are 12 pairs of cranial nerves which arise from the brain, and 31 pairs of spinal nerves which extend from the spinal cord. Cranial nerves are named I to XII, determined by their skull exit location (anterior to posterior). Spinal nerves are divided into 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal nerve, depending on vertebral level from which they arise. In certain areas of the body peripheral nerves interconnect, creating neural networks called plexuses. Notable plexuses are the:
• Cervical plexus (C1-C4) innervates:

  • Back of the head
  • Some neck muscles
  • Pericardium
  • Diaphragm
  • Via great auricular, transverse cervical nerve, lesser occipital, supraclavicular, and phrenic nerves
• Brachial plexus (C5-T1) innervates the upper limb with nerves such as:

  • Median
  • Ulnar
  • Radial
  • Musculocutaneous
  • Axillary nerve
• Lumbar plexus (L1-L4) innervates:

  • Muscles and skin of the abdomen and pelvis
  • Thigh muscles
  • Via iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, obturator, femoral nerves
• Sacral plexus (S1-S4, with branches from L4, L5) innervates:

  • Muscles and skin of parts of the pelvis, posterior thigh, lower leg, and foot
  • Via gluteal, sciatic, posterior femoral cutaneous, pudendal, nerve to piriformis, nerve to obturator internus, and nerve to quadratus femoris