Circulatory system

Skeletal muscles

Anatomy & Physiology - Body Systems
GM Diet Menu must be prepared well in advance, to keep the momentum going. The Cabbage Soup or Wonder Soup as it is popularly called is a wholesome food offering. Many different types of hemocytes have been described in different species, but they have been studied most extensively in insects, in which four major types and functions have been suggested: It is the major means of transport of nutrients, metabolites, excretory products, hormones, and gases, and it may provide the mechanical force for such diverse processes as hatching and molting in arthropods and burrowing in bivalve mollusks. Any text you add should be original, not copied from other sources. EMS works directly on the muscles, bypassing the body's energy conservation system, thus there's no limit to the percentage of fiber that can be activated. The series of events during which blood is passed through the heart is known as the cardiac cycle.

Skeletal System Physiology

The GM Diet Plan: Lose Your Excess Weight in Just 7 Days – GMDiet

Exercise works as a stimulus and gives stress to muscles. Effects of exercise on muscular system would benefit by increasing size and number of mitochondria, improved perception of muscle tone and also overall improved:. After exercise you may feel short term effects like: Blood flow because of increased volume of blood that is pumped to muscle tissue.

Muscle fatigue is short-term decline in the ability of a muscle to generate force. Another way to describe muscle fatigue is as the short-term inability to continue to repeat muscular contractions with the same force. Muscle exhaustion when exercise continues through muscle fatigue without rest after time it can lead to muscle exhaustion.

Muscle damage often happens, because of over-stretching without a proper warming-up or no warming-up before intense exercise. Cramp uncontrollable and very painful muscle contraction. After some time passes then long term effects on muscles takes place like: Muscle size increases mainly due to muscle ability to adapt to stress over a period of time which increases them in size.

This type of locomotion is seen most commonly in burrowing species, who move through the substratum almost exclusively by this means. Like the annelids, many mollusks, especially the more sedentary bivalves, set up local feeding and respiratory currents. Fluid movement through the mantle cavity normally depends on muscular pumping through inhalant and exhalant siphons.

Within the cavity itself, however, ciliary activity maintains continuous movement across the gill surfaces, collecting food particles and passing them to the mouth. The cephalopods are more active than other mollusks and consequently have higher metabolic rates and circulatory systems of a higher order of organization.

These systems are closed with distinct arteries, veins, and capillaries; the blood 6 percent of body weight remains distinct from the interstitial fluid 15 percent of body weight. These relative percentages of body weight to blood volume are similar to those of vertebrates and differ markedly from those of species with open circulatory systems, in which hemolymph may constitute 40 to 50 percent of body weight.

The cephalopod heart usually consists of a median ventricle and two auricles. Arterial blood is pumped from the ventricle through anterior and posterior aortas that supply the head and body, respectively.

It is passed through the capillary beds of the organs, is collected, and is returned to the heart through a major venous vessel, the vena cava. The vena cava bifurcates divides into two branches near the excretory organs, and each branch enters the nephridial sac before passing to the accessory hearts situated at the base of the gills.

Veins draining the anterior and posterior mantle and the gonads merge with the branches of the vena cava before reaching the branchial hearts. Contraction of the branchial hearts increases the blood pressure and forces blood through the gill capillaries.

The auricles then drain the gills of oxygenated blood. The blood of most mollusks, including cephalopods, contains hemocyanin , although a few gastropods use hemoglobin. In the cephalopods the pigment unloads at relatively high oxygen pressures, indicating that it is used to transport rather than store oxygen. Rapid cephalopod locomotion depends almost entirely on water pressure. During inhalation, muscular activity within the mantle wall increases the volume of the mantle cavity and water rushes in.

Contraction of the circular mantle muscles closes the edge of the mantle and reduces its volume, forcing the enclosed water through the mobile funnel at high pressure. The force of water leaving the funnel propels the animal in the opposite direction. Members of the phylum Brachiopoda lamp shells superficially resemble the mollusks but are not related.

The circulatory system of brachiopods is open and consists of a small contractile heart situated over the gut, from which anterior and posterior channels supply sinuses in the wall of the gut, the mantle wall, and the reproductive organs. The blood vascular system of arthropods is open.

The coelom is much reduced, and most of the spaces in the arthropod body are hemocoels. The tubular heart is dorsal and contained in a pericardial sinus. Blood is pumped from the heart through a series of vessels arteries that lead to the tissue sinuses.

Although the blood flows freely through the tissues it may, especially in the larger species, be directed by membranes along a more or less constant pathway. The blood collects in a ventral sinus from which it is conducted back to the heart through one or more venous channels. Variations in the circulatory patterns of the different classes of the phylum Arthropoda largely reflect the method of respiratory exchange and consequent function of the blood vascular system.

Most of the aquatic species of the class Crustacea have gills with a well-developed circulatory system, including accessory hearts to increase blood flow through the gills. A small number of species lack gills and a heart, and oxygen is absorbed through the body surface; bodily movements or peristaltic gut contractions circulate the blood within the tissue spaces.

In the mainly terrestrial class Insecta, the role of oxygen transport has been removed from the blood and taken over by the ramifying tracheal system that carries gaseous atmospheric oxygen directly to the consuming tissues. Insects are able to maintain the high metabolic rates necessary for flight while retaining a relatively inefficient circulatory system. Among the chelicerate possessing fanglike front appendages arthropods for example, scorpions, spiders, ticks, and mites , the horseshoe crab, Limulus , has a series of book gills gills arranged in membranous folds on either side of the body into which blood from the ventral sinus passes for oxygenation prior to return to the heart.

The largely terrestrial arachnids may have book lungs that occupy a similar position in the circulatory pathway, a tracheal system comparable to that of insects, or, in the case of smaller species, reduced tracheal and vascular systems in which contractions of the body muscles cause blood circulation through the sinus network.

The legs of spiders are unusual because they lack extensor muscles and because blood is used as hydraulic fluid to extend the legs in opposition to flexor muscles.

The blood pressure of a resting spider is equal to that of a human being and may double during activity. The high pressure is maintained by valves in the anterior aorta and represents an exception to the general rule that open circulatory systems only function at low pressure. The circulatory systems of echinoderms sea urchins, starfishes, and sea cucumbers are complicated as they have three largely independent fluid systems. The large fluid-filled coelom that surrounds the internal organs constitutes the major medium for internal transport.

Circulatory currents set up by the ciliated cells of the coelomic lining distribute nutrients from the gut to the body wall. Phagocytic coelomocytes are present, and in some species these contain hemoglobin.

The coelomic fluid has the same osmotic pressure as seawater, and the inability to regulate that pressure has confined the echinoderms to wholly marine habitats. The blood-vascular hemal system is reduced and consists of small, fluid-filled sinuses that lack a distinct lining. The system is most highly developed in the holothurians sea cucumbers , in which it consists of an anterior hemal ring and radial hemal sinuses.

The most prominent features are the dorsal and ventral sinuses, which accompany the intestine and supply it through numerous smaller channels. The dorsal sinus is contractile, and fluid is pumped through the intestinal sinuses into the ventral sinus and thence to the hemal ring. Most members of the class Holothuroidea have a pair of respiratory trees, located in the coelom on either side of the intestine, which act as the major sites for respiratory exchange.

Each tree consists of a main tubular trunk with numerous side branches, each ending in a small vesicle. Water is passed through the tubules by the pumping action of the cloaca. The branches of the left tree are intermingled with the intestinal hemal sinuses and provide a means of oxygenating the blood via the coelomic fluid. The right tree is free in the coelomic fluid and has no close association with the hemal system. Respiratory exchange in other echinoderms is through thin areas of the body wall, and the hemal system tends to be reduced.

The water vascular system of echinoderms is best developed in the starfishes and functions as a means of locomotion and respiratory exchange. The entire system consists of a series of fluid-filled canals lined with ciliated epithelium and derived from the coelom. The canals connect to the outside through a porous, button-shaped plate, called the madreporite , which is united via a duct the stone canal with a circular canal ring canal that circumvents the mouth.

Long canals radiate from the water ring into each arm. Lateral canals branch alternately from the radial canals, each terminating in a muscular sac or ampulla and a tube foot podium , which commonly has a flattened tip that can act as a sucker.

Contraction of the sac results in a valve in the lateral canal closing as the contained fluid is forced into the podium, which elongates. On contact with the substratum, the centre of the distal end of the podium is withdrawn, resulting in a partial vacuum and adhesion that is aided by the production of a copious adhesive secretion. Withdrawal results from contraction of the longitudinal muscles of the podia.

Among the phylum Hemichordata are the enteropneusts acornworms , which are worm-shaped inhabitants of shallow seas and have a short, conical proboscis , which gives them their common name. The vascular system of the Enteropneusta is open, with two main contractile vessels and a system of sinus channels. The colourless blood passes forward in the dorsal vessel, which widens at the posterior of the proboscis into a space, the contractile wall of which pumps the blood into the glomerulus , an organ formed from an in-tucking of the hind wall of the proboscis cavity.

From the glomerulus the blood is collected into two channels that lead backward to the ventral longitudinal vessel. This vessel supplies the body wall and gut with a network of sinuses that eventually drain back into the dorsal vessel. The phylum Chordata contains all animals that possess, at some time in their life cycles, a stiffening rod the notochord , as well as other common features. The subphylum Vertebrata is a member of this phylum and will be discussed later see below The vertebrate circulatory system.

All other chordates are called protochordates and are classified into two groups: The blood-vascular system of the tunicates , or sea squirts , is open, the heart consisting of no more than a muscular fold in the pericardium.

There is no true heart wall or lining and the whole structure is curved or U-shaped, with one end directed dorsally and the other ventrally. Each end opens into large vessels that lack true walls and are merely sinus channels. The ventral vessel runs along the ventral side of the pharynx and branches to form a lattice around the slits in the pharyngeal wall through which the respiratory water currents pass. Blood circulating through this pharyngeal grid is provided with a large surface area for gaseous exchange.

The respiratory water currents are set up by the action of cilia lining the pharyngeal slits and, in some species, by regular muscular contractions of the body wall. Dorsally, the network of pharyngeal blood vessels drains into a longitudinal channel that runs into the abdomen and breaks up into smaller channels supplying the digestive loop of the intestine and the other visceral organs.

The blood passes into a dorsal abdominal sinus that leads back to the dorsal side of the heart. The circulatory system of the sea squirt is marked by periodic reversals of blood flow caused by changes in the direction of peristaltic contraction of the heart. Sea squirt blood has a slightly higher osmotic pressure than seawater and contains a number of different types of amoebocytes, some of which are phagocytic and actively migrate between the blood and the tissues.

The blood of some sea squirts also contains green cells, which have a unique vanadium-containing pigment of unknown function. Amphioxus Branchiostoma lanceolatum is a cephalochordate that possesses many typical vertebrate features but lacks the cranial cavity and vertebral column of the true vertebrate. Its circulatory pattern differs from that of most invertebrates as the blood passes forward in the ventral and backward in the dorsal vessels. A large sac, the sinus venosus , is situated below the posterior of the pharynx and collects blood from all parts of the body.

The blood passes forward through the subpharyngeal ventral aorta, from which branches carry it to small, accessory, branchial hearts that pump it upward through the gill arches. The oxygenated blood is collected into two dorsal aortas that continue forward into the snout and backward to unite behind the pharynx. The single median vessel thus formed branches to vascular spaces and the intestinal capillaries.

Blood from the gut collects in a median subintestinal vein and flows forward to the liver , where it passes through a second capillary bed before being collected in the hepatic vein and passing to the sinus venosus. Paired anterior and posterior cardinal veins collect blood from the muscles and body wall. These veins lead, through a pair of common cardinal veins duct of Cuvier , to the sinus venosus.

There is no single heart in the amphioxus, and blood is transported by contractions that arise independently in the sinus venosus, branchial hearts, subintestinal vein, and other vessels. The blood is nonpigmented and does not contain cells; oxygen transport is by simple solution in the blood. We welcome suggested improvements to any of our articles. You can make it easier for us to review and, hopefully, publish your contribution by keeping a few points in mind.

Your contribution may be further edited by our staff, and its publication is subject to our final approval. Unfortunately, our editorial approach may not be able to accommodate all contributions.

Our editors will review what you've submitted, and if it meets our criteria, we'll add it to the article. Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed. Page 1 of 2.

Next page The vertebrate circulatory system. Learn More in these related Britannica articles: Modern reptiles do not have the capacity for the rapid sustained activity found in birds and mammals. It is generally accepted that this lower capacity is related to differences in the circulatory and respiratory systems. Before the origin of lungs, the vertebrate circulatory…. In mammals, as in birds, the right and left ventricles of the heart are completely separated, so that pulmonary lung and systemic body circulations are completely independent.

Oxygenated blood arrives in…. The circulatory system in the lower oligochaetes consists of a dorsal vessel that arises from a blood sinus or capillary network surrounding the intestine and conveys blood forward; a ventral vessel that conveys blood backward; and connective vessels between the two. The digestive canal consists of a tube, which is almost straight asteroids and ophiuroids , coiled in a clockwise direction crinoids and holothurians , or coiled first clockwise, then counterclockwise echinoids.

The tube may be divided into esophagus, stomach, intestine, and rectum. More About Circulatory system 21 references found in Britannica articles Assorted References adaptations in animals In animal: Circulatory organs work of Harvey In William Harvey: Discovery of circulation comparative anatomy arachnids In arachnid: Circulatory system scorpions In scorpion: Internal features spiders In spider: Circulation crustaceans In crustacean: The circulatory system annelids In annelid: Circulatory system arthropods In arthropod: Circulatory system birds In bird: Muscles and organs View More.

Articles from Britannica Encyclopedias for elementary and high school students. Help us improve this article! Contact our editors with your feedback. The humerus is the bone of the upper arm. It forms the ball and socket joint of the shoulder with the scapula and forms the elbow joint with the lower arm bones. The radius and ulna are the two bones of the forearm. The ulna is on the medial side of the forearm and forms a hinge joint with the humerus at the elbow.

The radius allows the forearm and hand to turn over at the wrist joint. The lower arm bones form the wrist joint with the carpals, a group of eight small bones that give added flexibility to the wrist.

The carpals are connected to the five metacarpals that form the bones of the hand and connect to each of the fingers. Each finger has three bones known as phalanges, except for the thumb, which only has two phalanges. Formed by the left and right hip bones, the pelvic girdle connects the lower limb leg bones to the axial skeleton. The femur is the largest bone in the body and the only bone of the thigh femoral region. The femur forms the ball and socket hip joint with the hip bone and forms the knee joint with the tibia and patella.

Commonly called the kneecap, the patella is special because it is one of the few bones that are not present at birth.

The patella forms in early childhood to support the knee for walking and crawling. The tibia and fibula are the bones of the lower leg. The fibula is mainly a muscle attachment point and is used to help maintain balance. The tibia and fibula form the ankle joint with the talus, one of the seven tarsal bones in the foot.

The tarsals are a group of seven small bones that form the posterior end of the foot and heel. The tarsals form joints with the five long metatarsals of the foot. Then each of the metatarsals forms a joint with one of the set of phalanges in the toes. Each toe has three phalanges, except for the big toe, which only has two phalanges. Living bone cells are found on the edges of bones and in small cavities inside of the bone matrix.

Although these cells make up very little of the total bone mass, they have several very important roles in the functions of the skeletal system. The bone cells allow bones to:. All of the bones of the body can be broken down into five types: The long bones of the body contain many distinct regions due to the way in which they develop. At birth, each long bone is made of three individual bones separated by hyaline cartilage.

The epiphyses and diaphysis grow towards one another and eventually fuse into one bone. Once the long bone parts have fused together, the only hyaline cartilage left in the bone is found as articular cartilage on the ends of the bone that form joints with other bones.

The articular cartilage acts as a shock absorber and gliding surface between the bones to facilitate movement at the joint. Looking at a bone in cross section, there are several distinct layered regions that make up a bone. The outside of a bone is covered in a thin layer of dense irregular connective tissue called the periosteum. The periosteum contains many strong collagen fibers that are used to firmly anchor tendons and muscles to the bone for movement.

Stem cells and osteoblast cells in the periosteum are involved in the growth and repair of the outside of the bone due to stress and injury. Blood vessels present in the periosteum provide energy to the cells on the surface of the bone and penetrate into the bone itself to nourish the cells inside of the bone. The periosteum also contains nervous tissue and many nerve endings to give bone its sensitivity to pain when injured. Deep to the periosteum is the compact bone that makes up the hard, mineralized portion of the bone.

Compact bone is made of a matrix of hard mineral salts reinforced with tough collagen fibers.

Navigation menu