Muscular system

The human muscles, seen from the front. 19th century illustration.
Three distinct types of muscle (L to R): Smooth (non-striated) muscle in internal organs, cardiac or heart muscle, and skeletal muscle.
Skeletal muscles, viewed from the front
Skeletal muscles, viewed from the back

Organ system consisting of skeletal, smooth, and cardiac muscle.

- Muscular system
The human muscles, seen from the front. 19th century illustration.

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A top-down view of skeletal muscle

Skeletal muscle

A top-down view of skeletal muscle
3D rendering of a skeletal muscle fiber
Muscle types by fiber arrangement
Types of pennate muscle. A – unipennate; B – bipennate; 
C – multipennate
ATPase staining of a muscle cross section. Type II fibers are dark, due to the alkaline pH of the preparation. In this example, the size of the type II fibers is considerably less than the type I fibers due to denervation atrophy.
Structure of muscle fibre showing a sarcomere under electron microscope with schematic explanation.
Diagram of sarcoplasmic reticulum with terminal cisternae and T-tubules.
Human embryo showing somites labelled as primitive segments.
When a sarcomere contracts, the Z lines move closer together, and the I band becomes smaller. The A band stays the same width. At full contraction, the thin and thick filaments overlap.
Contraction in more detail
(a) Some ATP is stored in a resting muscle. As contraction starts, it is used up in seconds. More ATP is generated from creatine phosphate for about 15 seconds. (b) Each glucose molecule produces two ATP and two molecules of pyruvic acid, which can be used in aerobic respiration or converted to lactic acid. If oxygen is not available, pyruvic acid is converted to lactic acid, which may contribute to muscle fatigue. This occurs during strenuous exercise when high amounts of energy are needed but oxygen cannot be sufficiently delivered to muscle. (c) Aerobic respiration is the breakdown of glucose in the presence of oxygen (O2) to produce carbon dioxide, water, and ATP. Approximately 95 percent of the ATP required for resting or moderately active muscles is provided by aerobic respiration, which takes place in mitochondria.
Exercise-induced signaling pathways in skeletal muscle that determine specialized characteristics of slow- and fast-twitch muscle fibers
Jogging is one form of aerobic exercise.
In muscular dystrophy, the affected tissues become disorganized and the concentration of dystrophin (green) is greatly reduced.
Prisoner of war exhibiting muscle loss as a result of malnutrition.

Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system that are mostly attached by tendons to bones of the skeleton.

Many of the internal organs of the human body

Organ (biology)

Organ is a collection of tissues joined in a structural unit to serve a common function.

Organ is a collection of tissues joined in a structural unit to serve a common function.

Many of the internal organs of the human body
The liver and gallbladder of a sheep
Relationship of major animal lineages with indication of how long ago these animals shared a common ancestor. On the left, important organs are shown, which allows us to determine how long ago these may have evolved.
The flower is the angiosperm's reproductive organ. This Hibiscus flower is hermaphroditic, and it contains stamen and pistils.
Strobilus of Equisetum telmateia
Human viscera

Muscular system: movement with muscles.

Features of the human activity system from the 1911 Encyclopædia Britannica

Human musculoskeletal system

Features of the human activity system from the 1911 Encyclopædia Britannica
The body contains three types of muscle tissue: (a) skeletal muscle, (b) smooth muscle, and (c) cardiac muscle.
On the anterior and posterior views of the muscular system above, superficial muscles (those at the surface) are shown on the right side of the body while deep muscles (those underneath the superficial muscles) are shown on the left half of the body. For the legs, superficial muscles are shown in the anterior view while the posterior view shows both superficial and deep muscles.
Human synovial joint composition

The human musculoskeletal system (also known as the human locomotor system, and previously the activity system) is an organ system that gives humans the ability to move using their muscular and skeletal systems.

Female (left) and male (right) adult human bodies photographed in ventral (above) and dorsal (below) perspectives. Naturally-occurring pubic, body, and facial hair has been deliberately removed to show anatomy

Human body

Structure of a human being.

Structure of a human being.

Female (left) and male (right) adult human bodies photographed in ventral (above) and dorsal (below) perspectives. Naturally-occurring pubic, body, and facial hair has been deliberately removed to show anatomy
Diagram of the human heart
Digestive system
Skin
Nervous system
Internal gross anatomy of the male reproductive system
External female reproductive system with mons pubis highlighted
Internal gross anatomy of the female reproductive system
Female urinary system
Cavities of human body
Baby being carried
Anatomical study by Leonardo da Vinci
Figure drawing by Lovis Corinth (before 1925)
Two facing pages of text with woodcuts of naked male and female figures, in the Epitome by Andreas Vesalius, 1543

This system can be split up into the muscular system and the skeletal system.

Adipose tissue is one of the main types of connective tissue.

Adipose tissue

Loose connective tissue composed mostly of adipocytes.

Loose connective tissue composed mostly of adipocytes.

Adipose tissue is one of the main types of connective tissue.
Distribution of white adipose in the human body
The obese mouse on the left has large stores of adipose tissue. It is unable to produce the hormone leptin. This causes the mouse to be hungry and eat more, which results in obesity. For comparison, a mouse with a normal amount of adipose tissue is shown on the right.
Abdominal obesity in men ("beer belly")
Micro-anatomy of subcutaneous fat
Brown fat cell
Diagrammatic sectional view of the skin (magnified).
White adipose tissue in paraffin section
Electronic instrument of body fat meter

In humans, adipose tissue is located: beneath the skin (subcutaneous fat), around internal organs (visceral fat), in bone marrow (yellow bone marrow), intermuscular (Muscular system) and in the breast (breast tissue).

Portrait of Steno as bishop (1868)

Nicolas Steno

Danish scientist, a pioneer in both anatomy and geology who became a Catholic bishop in his later years.

Danish scientist, a pioneer in both anatomy and geology who became a Catholic bishop in his later years.

Portrait of Steno as bishop (1868)
Portrait of Niels Steensen (1666–1677). Unsigned but attributed to court painter Justus Sustermans. (Uffizi Gallery, Florence, Italy)
Elementorum myologiae specimen: Illustration from Steensen's 1667 paper comparing the teeth of a shark head with a fossil tooth
De solido intra solidum naturaliter contento dissertationis prodromus (1669)

In Florence Steensen focused on the muscular system and the nature of muscle contraction.

Detection of numerous ragged red fibers in a muscle biopsy

Leigh syndrome

Inherited neurometabolic disorder that affects the central nervous system.

Inherited neurometabolic disorder that affects the central nervous system.

Detection of numerous ragged red fibers in a muscle biopsy
Two healthy mitochondria from mammalian lung tissue as shown by electron microscopy
The autosomal recessive pattern of inheritance seen in some cases of Leigh syndrome
The X-linked recessive pattern of inheritance seen occasionally in cases of Leigh syndrome.

As the disease progresses, the muscular system is debilitated throughout the body, as the brain cannot control the contraction of muscles.

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VX (nerve agent)

Extremely toxic synthetic chemical compound in the organophosphorus class, specifically, a thiophosphonate.

Extremely toxic synthetic chemical compound in the organophosphorus class, specifically, a thiophosphonate.

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P–S cleavage (non-toxic products)
P-O cleavage (EA-2192 product is still toxic)
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On such exposure, these agents severely disrupt the body's signaling between the nervous and muscular systems, leading to a prolonged neuromuscular blockade, flaccid paralysis of all the muscles in the body including the diaphragm, and death by asphyxiation.

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Index of anatomy articles

Articles related to anatomy include:

Articles related to anatomy include:

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muscular system

Incontinentia pigmenti forming along Blaschko's lines in a 3-year-old girl

Blaschko's lines

Blaschko's lines, also called the lines of Blaschko, are lines of normal cell development in the skin.

Blaschko's lines, also called the lines of Blaschko, are lines of normal cell development in the skin.

Incontinentia pigmenti forming along Blaschko's lines in a 3-year-old girl

They do not correspond to nervous, muscular, or lymphatic systems.