Skeletal System

Examples of Skeletal System in the following topics:

• Divisions of the Skeletal System: Axial and Appendicular

  • The skeletal system is divided into two distinct divisions: the axial skeleton and the appendicular system.
  • The skeletal system serves many important functions.
  • The number of bones in the human skeletal system is a controversial topic.

• Overview of the Musculoskeletal System

  • The musculoskeletal system is an organ system enabling an organism to move, support itself, and maintain stability during locomotion.
  • The musculoskeletal system (also known as the locomotor system) is an organ system that gives animals (including humans) the ability to move, using the muscular and skeletal systems.
  • The skeletal portion of the system serves as the main storage system for calcium and phosphorus.
  • The skeleton also contains critical components of the hematopoietic (blood production) system.
  • Skeletal muscles are attached to bones and arranged in opposing groups around joints.

• Comparing the Somatic and Autonomic Nervous Systems

  • The peripheral nervous system (PNS, see ) is divided into the somatic nervous system and the autonomic nervous system.
  • The somatic nervous system (SoNS) is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles.
  • The SoNS consists of efferent nerves responsible for stimulating muscle contraction, including all the non-sensory neurons connected with skeletal muscles and skin.
  • The somatic nervous system controls all voluntary muscular systems within the body, and also mediates involuntary reflex arcs.
  • The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.

• Local Regulation of Blood Flow

  • For example, more blood is directed to the skeletal muscles, brain, or digestive system when they are active, and blood flow to the skin can be reduced or increased to aid with thermoregulation.
  • This regulation can be systemic, affecting the whole of the circulatory system, or localized to specific tissues or organs.
  • As such arterioles are the main part of the circulatory system in which local control of blood flow occurs.
  • They are innervated and so can respond to nervous system stimuli and also various circulating hormones.
  • However, the arterioles of skeletal muscle, cardiac muscle, and the pulmonary circulation vasodilate in response to these hormones acting on beta-adrenergic receptors.

• Structure of the Lymphatic System

  • In a sense, it is a circulatory system for lymph fluid and the site of many key immune system functions.
  • The structure of the lymphatic system facilitates these general roles.
  • The lymphatic vessels are the lymphatic system equivalent to the blood vessels of the circulatory system and drains fluid from the circulatory system.
  • The lymphatic system is an active pumping system with active pumping segments with a function similar to that of peristalsis.
  • Skeletal muscle contractions also move lymph through the vessels.

• Slow-Twitch and Fast-Twitch Muscle Fibers

  • Skeletal muscle contains different fibers which allowing for both rapid short-term and slower, repeatable long-term contractions.
  • Skeletal muscle fibers can be further subdivided into slow and fast-twitch subtypes depending on their metabolism and corresponding action.
  • However, this reaction requires the delivery of large amounts oxygen to the muscle which can rapidly become rate limiting if the respiratory and circulatory systems cannot keep up.
  • Regardless, repeated exercise that prioritizes one type of muscle fiber use over the other can lead to improvements in an individual’s ability to perform that activity through alterations in fiber composition and number associated with improvements in associated systems such as respiration and circulation.
  • Describe the different types of skeletal muscle fibers and their respective functions.

• Interactions of Skeletal Muscles

  • Skeletal muscles interact to produce movements by way of anatomical positioning and the coordinated summation of innervation signals.
  • Skeletal muscle contractions can be grouped based on the length and frequency of contraction.
  • When a weak signal is sent by the central nervous system to contract a muscle, the smaller motor units, being more excitable than the larger ones, are stimulated first.
  • For skeletal muscles, the force exerted by the muscle can be controlled by varying the frequency at which action potentials are sent to muscle fibers.
  • Explain the summation interactions of skeletal muscles and how they affect movement

• Arrangement of Fascicles

  • Skeletal muscles are grouped into fascicles, which are bunches of muscle fibers surrounded by a perimysium.
  • Skeletal muscle tissue is composed of numerous muscle fibers which are separated from adjacent muscles and other tissues by a layer of dense, elastic connective tissue termed the fascia.
  • Key groups of muscle and the associated vascular and nervous systems can also be separated from other tissue, for example in the upper arm, with these groupings termed fascial compartments.
  • It also maintains the required close association of the vascular and nervous system with the muscle which are required to deliver required metabolites and nerve impulses.
  • Skeletal muscle is surrounded by a thick outer layer of connective tissue termed the fascia.

• Muscle Development

  • The ectoderm eventually forms the skin (including hair and nails), mucous membranes, and nervous system.
  • The mesoderm forms the skeleton and muscles, heart and circulatory system, urinary and reproductive systems, and connective tissues inside the body.
  • Expression of skeletal alpha-actin is also regulated by the Androgen Receptor.
  • The fusion of myoblasts is specific to skeletal muscle (e.g., biceps brachii) and not cardiac or smooth muscle.
  • There are various specialized forms of myocytes: cardiac, skeletal, and smooth muscle cells, with various properties.

• Autonomic Interactions

  • The sympathetic and parasympathetic autonomic nervous systems cooperatively modulate internal physiology to maintain homeostasis.
  • More generally, these two systems should be seen as permanently modulating vital functions, in usually antagonistic fashion, to achieve homeostasis.
  • Some typical actions of the sympathetic and parasympathetic systems are listed below.
  • In the autonomic nervous system, preganglionic neurons connect the CNS to the ganglion.
  • Describe the interactions between the sympathetic and parasympathetic divisions of the autonomic nervous system