Logan Steele
Cutaneous muscles are muscles that lie in the subcutaneous tissue and attach to the skin. They may or may not have a bony attachment. Facial expressions, such as smiling and winking, are produced by cutaneous muscles. The arrector pili muscles, or hair erector muscles, are the smallest skeletal muscles in the body and are found in all areas of the skin that contain hair follicles. These muscles control the positioning of hairs and the activity of sebaceous glands in response to environmental factors such as temperature.
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What You'll Learn
Cutaneous maximus muscle
A cutaneous muscle is a muscle that lies in the subcutaneous tissue and attaches to the skin. These muscles are responsible for producing facial expressions such as smiles and winks. The skin is the body's largest organ, covering the entire outside of the body and weighing approximately six pounds. It forms a protective barrier against pathogens and injuries from the environment.
The cutaneous maximus muscle (CMM) is a cutaneous muscle that twitches the skin. It has been observed in rats and mice for research purposes. The CMM has mixed muscle types and similar anatomic dimensions to the latissimus dorsi muscle. It provides ample tissue for pharmacological and biochemical studies and is easier to dissect than the latissimus flap, making it a very useful experimental model for flap transfer research.
The microvascular transplantation of the CMM flap has been performed on rats at the groin site, with anastomosis of the axillary vessels to the appropriate femoral vessels. This procedure has a high success rate, a relatively long pedicle length, and microsurgical procedures can be performed in a short period. The donor site deficit does not impair animal mobility, and no evidence of limb ischemia was noted after ligation of the axillary vessels.
The lateral thoracic nerve (LTN) innervates the CMM with some of the shortest and longest motor nerve fibres in the mouse body. The branching pattern of the LTN and its innervation of the CMM can be observed through imaging techniques. This has been used to study nerve degeneration and regeneration over time after LTN crush by morphological and electrophysiological analyses.
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Muscles of expression
A cutaneous muscle is a muscle that lies in the subcutaneous tissue and attaches to the skin. It may or may not have a bony attachment. The muscles of expression are the chief examples of cutaneous muscles in humans. Facial expression muscles are skeletal muscles that are found in all vertebrate orders and are derived from the hyoid branchiomeric arch. They are distinguished from other cranial musculature by their innervation via the seventh cranial nerve.
The muscles of facial expression, also known as mimetic muscles, can generally be divided into three main functional categories. These striated muscles broadly originate from the surface of the skull and insert into facial skin. Their contraction pulls on the skin and exerts effects on facial expressions. The muscles of facial expression are involved in various activities, such as mastication, vision, and respiration, but their major role is in nonverbal communication, such as close-proximity social signaling and mate recognition. This role is especially important in the Primate order, where close-range social signaling and communication among individuals are more common than in most other mammals.
The facial muscles are the only group of muscles that insert into the skin. They are located in the subcutaneous tissue, originating from bone or fascia. Humans are capable of making 10,000 unique facial expressions. In the 1960s, American psychologist Paul Ekman disproved theories that human expressions were learned. Instead, he showed that our facial expressions are innate and universal.
The facial nerve innervates the frontalis and the posterior auricular branch of the facial nerve innervates the occipitalis. The occipital belly is supplied by the occipital artery and the frontal belly is supplied by the orbital orbicularis, palpebral orbicularis, and lacrimal orbicularis. The orbital section requires conscious effort, while the lacrimal section controls the tear pump mechanism that filters into the lacrimal sac.
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Muscle contraction
The cutaneus trunci muscle (CTM) is a thin, broad sheet of skeletal muscle that originates bilaterally on the humerus and is inserted beneath the dermis of the back and flank skin. A nociceptive stimulus applied to the skin elicits a localized reflex contraction in that region of the CTM underlying the site of sensory stimulation.
The mechanism of muscle contraction can be summarized in three steps:
- A message travels from the nervous system to the muscular system, triggering chemical reactions.
- The chemical reactions lead to the muscle fibers reorganizing themselves in a way that shortens the muscle—that’s the contraction.
- When the nervous system signal is no longer present, the chemical process reverses, and the muscle fibers rearrange again and the muscle relaxes.
The striated muscles in our body comprise many individual muscle fibers. Inside these muscle fibers are smaller units called myofibrils, made of parallel thin and thick filaments. These filaments are arranged longitudinally in small units known as sarcomeres, which give the muscle a striated appearance under microscopy.
The thin filaments are composed of actin, tropomyosin, and troponin. Actin is a globular protein that combines with other actin globules to form two intertwined strands with positive and negative ends. The double-stranded actin filaments are covered by tropomyosin, which blocks the interaction between myosin and actin when the muscle is inactive.
The complex process leading to muscle contraction, called excitation-contraction coupling, begins when an action potential causes depolarization in the myocyte membrane. The depolarization is spread via the transverse (T) tubules, which help spread depolarization signals to the entire muscle fiber.
Cross-bridge cycling begins when ATP binds to an ATP-binding domain on the myosin head. Myosin dissociates from the actin, breaking the cross-bridge. ATP is then hydrolyzed into ADP and P, which causes the myosin heads to change conformation and move toward the positive end of the actin, cocking the myosin head. The phosphate is released, and the ADP-bound myosin binds to a new location on the actin filament. ADP is then released, causing the myosin to return to its original position, pulling on the actin filament and causing the sarcomere (and, therefore, the muscle fiber) to contract.
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Subcutaneous fat
The skin is the body's largest organ, covering the entire outside of the human body. It is about 2mm thick and weighs approximately six pounds. The skin is made up of three layers: the epidermis, the dermis, and the subcutis or hypodermis, which is the deepest layer of fat found just beneath the skin. This layer of subcutaneous fat is also referred to as the subcutaneous tissue or subcutaneous muscle.
The amount of subcutaneous fat a person has depends on a combination of genetics and lifestyle factors. Everyone is born with subcutaneous fat, and genetics determine the initial amount. However, environmental factors also play a significant role in the development of subcutaneous fat over time. Lifestyle factors such as diet and physical activity influence the amount of subcutaneous fat. A diet high in fatty foods and low in lean proteins, whole grains, low-fat dairy, fruits, and vegetables can contribute to increased subcutaneous fat. Similarly, an inactive lifestyle or lack of aerobic activity can lead to a higher amount of subcutaneous fat.
While some subcutaneous fat is normal and harmless, excess fat can lead to serious health issues. Excess subcutaneous fat can be a sign of having more fat overall, including visceral fat, which is associated with numerous diseases. People with large amounts of subcutaneous fat are at a higher risk of obesity-related diseases, including heart disease, diabetes, and stroke. Therefore, it is important to manage subcutaneous fat levels through a healthy diet and regular exercise.
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Striated muscle
Cutaneous muscles are muscles that lie in the subcutaneous tissue and attach to the skin. They may or may not have a bony attachment. The muscles of expression are the chief examples of cutaneous muscles in humans. One example of a cutaneous muscle is the arrector pili muscle, which is a tiny muscle connected to each hair follicle and the skin.
Skeletal muscles are also known as voluntary muscles, as we can control how and when they move. They are composed of skeletal muscle fibres, blood vessels, nerve fibres, and connective tissue. Each muscle fibre contains sarcolemma, sarcoplasm, and sarcoplasmic reticulum, and the functional unit of a muscle fibre is the sarcomere. Skeletal muscle cells have many nuclei, while cardiac and smooth muscle cells have only one.
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Frequently asked questions
A cutaneous muscle is a muscle that lies in the subcutaneous tissue and attaches to the skin. It may or may not have a bony attachment.
The arrector pili muscle, also known as the hair erector muscle, is a cutaneous muscle. It is a tiny muscle connected to each hair follicle and the skin. The muscles of expression are also cutaneous muscles.
There are three types of muscles: involuntary, voluntary, and cardiac, composed of smooth, striated, and mixed smooth and striated tissue, respectively.
Cutaneous muscles, such as the arrector pili muscle, control the positioning of hairs and the activity of sebaceous glands in response to environmental stimuli like temperature changes.
