Logan Steele
The human body has over 600 muscles, which are pieces of soft tissue that help us move, breathe, swallow and stay alive. There are three types of muscles: skeletal, smooth, and cardiac. Skeletal muscles are the most common type, comprising 30-40% of our total body mass. They are attached to bones by tendons and come in various shapes and sizes. They are also often striped or striated. Smooth muscles, on the other hand, have a very smooth, uniform appearance under a microscope and are found inside organs like the stomach and intestines. Lastly, cardiac muscles make up the middle layers of the heart and are responsible for pumping blood throughout the body. They are also striated but have a banded appearance that contrasts with the smooth muscles.
| Characteristics | Values |
|---|---|
| Number of muscles in the human body | More than 600 |
| Muscle composition | Thousands of small fibres woven together |
| Muscle tissue types | Skeletal, smooth, and cardiac |
| Skeletal muscle fibres | Red and white |
| Skeletal muscle appearance | Striated or striped |
| Cardiac muscle appearance | Striated |
| Smooth muscle appearance | Smooth and uniform |
| Muscle shapes | Spindle, flat, triangular, and circular |
| Muscle functions | Pumping blood, supporting movement, lifting heavy weights, giving birth |
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What You'll Learn
Skeletal muscles are attached to bones by tendons
The human body is made up of more than 600 muscles, which help us do everything from pumping blood around our bodies to lifting heavy weights. Muscles are pieces of soft tissue made up of thousands of small fibres woven together. These fibres stretch and press together to move our organs and bodies.
Skeletal muscles are the most common type of muscle in the body, comprising 30% to 40% of our total body mass. They are attached to bones by tendons, which are tough bands of dense regular connective tissue with strong collagen fibres that firmly attach muscles to bones. Tendons are woven into the coverings of both muscles and bones, and they are under extreme stress when muscles pull on them, so they are very strong.
Skeletal muscles are voluntary muscles, meaning we control how and when they move and work. They are attached to the bones all over our bodies and allow us to perform a wide range of movements and functions. They are called skeletal muscles because they always connect to the skeleton in at least one place, and most are attached to two bones through tendons.
The muscles in our face are an example of skeletal muscles. Unlike the rest of the body, facial muscles don't all attach directly to bone. Instead, many of them attach under the skin, allowing us to contract our facial muscles just a tiny bit and make dozens of different expressions.
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Cardiac muscle makes up the middle layers of the heart
The human body has over 600 muscles, some of which are visible and some of which work silently to keep us alive. One such vital yet invisible muscle is the cardiac muscle, which forms the middle layer of the heart.
Also known as the myocardium, the cardiac muscle is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. The myocardium is a thick layer of muscle tissue that forms the bulk of the heart. It is sandwiched between the inner endocardium and the outer epicardium (also known as the visceral pericardium). The endocardium is not cardiac muscle, but simple squamous epithelial cells that form the inner lining of the heart chambers and valves. The epicardium forms part of the pericardial sac that surrounds, protects, and lubricates the heart.
The cardiac muscle is composed of individual cardiac muscle cells or cardiomyocytes, which are joined by intercalated discs. These cardiomyocytes are the contractile cells that allow the heart to pump. They are tubular structures composed of chains of myofibrils, which are rod-like units within the cell. The myofibrils consist of repeating sections of sarcomeres, which are the fundamental contractile units of the muscle cells. Sarcomeres are composed of long proteins that organize into thick and thin filaments, called myofilaments. The thick myofilaments contain the protein myosin, while the thin myofilaments contain the protein actin. When the muscle contracts, the myofilaments slide past each other, producing the formation of "cross-bridges", which causes contraction of the heart and generates force.
The cardiac muscle is an involuntary, striated muscle that contracts in a similar manner to skeletal muscle. However, the contraction of the cardiac muscle differs from skeletal muscle in that it is spontaneous and rapid. The cardiac muscle stimulates itself to contract, although hormones and signals from the brain can adjust the rate of contraction. This rapid, involuntary contraction and relaxation of the cardiac muscle are vital for pumping blood throughout the cardiovascular system.
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Smooth muscle is found in the stomach and intestines
The human body is made up of more than 600 muscles that help us move, breathe, swallow, and stay alive. There are three types of muscles in the human body: skeletal, cardiac, and smooth muscles. Smooth muscles are involuntary muscles that line the inside of some organs. They are found in the walls of hollow organs, such as the intestines, uterus, and stomach. They are also found in the walls of passageways, including arteries and veins of the cardiovascular system. Smooth muscles play an important role in the tracts of the urinary, respiratory, and reproductive systems.
Smooth muscles have a very smooth, uniform appearance when viewed under a microscope, in contrast to the banded appearance of skeletal and cardiac muscles. They are also known as visceral muscles, which is the weakest of all muscle tissues. Smooth muscles cannot be controlled consciously and are instead controlled by the unconscious part of the brain.
Smooth muscles found in the stomach and intestines help with digestion and nutrient collection. They produce tonic contractions that maintain organ dimension and forceful contractions that propel food along the gastrointestinal tract. Smooth muscles also play a role in the regulation of blood pressure and tissue oxygenation.
Smooth muscles are an integral part of the human body, and their function is required for life. They are found in almost every organ system and perform a variety of functions. Smooth muscles in the intestinal wall, for example, help move waste through the intestines and aid in lung expansion during breathing.
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Facial muscles attach under the skin
The human body has over 600 muscles, some of which are visible and some of which are internal, helping us to move, breathe, swallow and stay alive. The facial muscles are a group of skeletal muscles that attach to the skull bone and control facial expressions. There are around 20 of these muscles on each side of the face, which are essential for chewing and making facial expressions.
Facial muscles, also known as mimetic muscles, are striated muscles that link the facial skin to the skull bone. They are the only muscles that attach to the dermis, just under the skin, and when they contract, the skin moves. These muscles also cause wrinkles at right angles to the muscles' action line. The facial muscles are supplied by the facial nerve (cranial nerve VII), with each nerve serving one side of the face.
Facial muscles are located throughout the face, including the ears, mouth, forehead, nose and eyes. They run underneath the skin from the scalp down to the neck. These muscles are part of the musculoskeletal system and contain elastic fibres that allow them to contract. Some of the fibres look dark and some look light, so they appear striped (striated) red and white when viewed under a microscope.
Facial muscles generally originate from the surface of the skull bone, rarely the fascia, and insert on the skin of the face. They start to develop in the fourth week from the first and second branchial arches, with the arches representing the branchial apparatus' mesodermal components. The branchial clefts contain ectoderm and become skin, while the branchial pouches contain endoderm, which becomes the mucosal lining.
Facial muscles are also important in reconstructive surgery, particularly in rehabilitating paralysed areas. CN VII nerve dysfunction weakens an entire side of the face, and transferring a CN V3-innervated muscle may provide a viable reanimation approach in severe cases.
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Muscles come in different shapes, like triangular or circular
The human body has more than 600 muscles, which help us do everything from pumping blood around our bodies to lifting heavy weights. These muscles come in different shapes and sizes, with four main shapes being spindle, flat, triangular, and circular.
Spindle-shaped muscles are wide through the middle and tapered at both ends, like the biceps on the front of the upper arm. Flat muscles are sheet-like, such as the diaphragm that separates the chest from the abdominal cavity. Triangular muscles are wider at the bottom and tapered at the top, like the deltoid muscles of the shoulder. Circular muscles are ring-shaped, like the muscles that surround the mouth, pupils, and anus, also known as sphincters.
Skeletal muscles, which are the most common type of muscle in the body, are often attached to the bones and help with movement, posture, and balance. They come in various shapes, including triangular deltoids and diamond-shaped rhomboid majors. Cardiac muscles, which make up the heart, are striated and have a banded appearance. Smooth muscles, on the other hand, have a very smooth and uniform appearance under a microscope.
The shape and size of muscles can vary depending on their function and location in the body. For example, the gluteal region contains three muscles differentiated by size: the gluteus maximus (large), gluteus medius (medium), and gluteus minimus (smallest). Facial muscles, which attach under the skin rather than directly to bone, allow us to make a wide range of expressions by contracting just a tiny bit.
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Frequently asked questions
The human body has over 600 muscles.
Muscles are pieces of soft tissue that help the body move, breathe, swallow and stay alive. They vary in size, shape and arrangement of fibres. Some muscles are broad, while others are narrow. Some muscles have fibres that are parallel to the long axis of the muscle, while others converge to a narrow attachment or are oblique.
Skeletal muscles are red and white and look striated, or striped. They are made up of hundreds of thousands of muscle cells, or fibres, that act together to perform the functions of the specific muscle they are a part of. Each muscle cell is a single cylindrical muscle cell.
Cardiac muscles are striated and make up the middle layers of the heart. They cannot be controlled consciously and are therefore involuntary muscles.
Smooth muscles are involuntary muscles that line the inside of some organs. They have a very smooth, uniform appearance when viewed under a microscope.
