Dermis in the context of "Ground substance"

Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals.The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and fine vellus hair. Most common interest in hair is focused on hair growth, hair types, and hair care, but hair is also an important biomaterial primarily composed of protein, notably alpha-keratin.

Attitudes towards different forms of hair, such as hairstyles and hair removal, vary widely across different cultures and historical periods, but it is often used to indicate a person's personal beliefs or social position, such as their age, gender, or religion.

Wound healing refers to a living organism's replacement of destroyed or damaged tissue by newly produced tissue.

In undamaged skin, the epidermis (surface, epithelial layer) and dermis (deeper, connective layer) form a protective barrier against the external environment. When the barrier is broken, a regulated sequence of biochemical events is set into motion to repair the damage. This process is divided into predictable phases: blood clotting (hemostasis), inflammation, tissue growth (cell proliferation), and tissue remodeling (maturation and cell differentiation). Blood clotting may be considered to be part of the inflammation stage instead of a separate stage.

Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among individuals is caused by variation in pigmentation, which is largely the result of genetics (inherited from one's biological parents), and in adults in particular, due to exposure to the sun, disorders, or some combination thereof. Differences across populations evolved through natural selection and sexual selection, because of social norms and differences in environment, as well as regulation of the biochemical effects of ultraviolet radiation penetrating the skin.

Human skin color is influenced greatly by the amount of the pigment melanin present. Melanin is produced within the skin in cells called melanocytes; it is the main determinant of the skin color of darker-skin humans. The skin color of people with light skin is determined mainly by the bluish-white connective tissue under the dermis and by the hemoglobin circulating in the veins of the dermis. The red color underlying the skin becomes more visible, especially in the face, when, as a consequence of physical exercise, sexual arousal, or the stimulation of the nervous system (e.g. due to anger or embarrassment), arterioles dilate. Color is not entirely uniform across an individual's skin; for example, the skin of the palm and the soles of the feet is lighter than most other skin; this is more noticeable in darker-skinned people.

Snakeskin may either refer to the skin of a live snake, the shed skin of a snake after molting, or to a type of leather that is made from the hide of a dead snake. Snakeskin and scales can have varying patterns and color formations, providing protection via camouflage from predators. The colors and iridescence in these scales are largely determined by the types and amount of chromatophores located in the dermis of the snake skin. The snake's skin and scales are also an important feature to their locomotion, providing protection and minimizing friction when gliding over surfaces.

The hair follicle is an organ found in mammalian skin. It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a complex interaction between hormones, neuropeptides, and immune cells. This complex interaction induces the hair follicle to produce different types of hair as seen on different parts of the body. For example, terminal hairs grow on the scalp and lanugo hairs are seen covering the bodies of fetuses in the uterus and in some newborn babies. The process of hair growth occurs in distinct sequential stages: anagen is the active growth phase, catagen is the regression of the hair follicle phase, telogen is the resting stage, exogen is the active shedding of hair phase and kenogen is the phase between the empty hair follicle and the growth of new hair.

The function of hair in humans has long been a subject of interest and continues to be an important topic in society, developmental biology and medicine. Of all mammals, humans have the longest growth phase of scalp hair compared to hair growth on other parts of the body. For centuries, humans have ascribed esthetics to scalp hair styling and dressing and it is often used to communicate social or cultural norms in societies. In addition to its role in defining human appearance, scalp hair also provides protection from UV sun rays and is an insulator against extremes of hot and cold temperatures. Differences in the shape of the scalp hair follicle determine the observed ethnic differences in scalp hair appearance, length and texture.

The integumentary system is the set of organs forming the outermost layer of an animal's body, comprising the skin, hair, scales, feathers, hooves, claws, and nails. It acts as a protective physical barrier between the external environment and the internal environment. Additionally, it maintains water balance, protects the deeper tissues, excretes waste, regulates body temperature, and contains the sensory receptors that detect pain, sensation, pressure, and temperature.

The skin (integument) is a composite organ, made up of at least two major layers of tissue: the outermost epidermis and the inner dermis, which are separated by a basement membrane (comprising basal lamina and reticular lamina). The epidermis comprises five layers: the stratum corneum, stratum granulosum, stratum spinosum and stratum basale. Where the skin is thicker, such as in the palms and soles, there is an extra layer of skin between the stratum corneum and the stratum granulosum known as the stratum lucidum. The dermis comprises two sections, the papillary and reticular layers, and contains connective tissues, blood vessels, glands, follicles, hair roots, sensory nerve endings, and muscular tissue. Between the integument and the deep body musculature there is a transitional subcutaneous zone, the hypodermis.

An ulcer is a sore on the skin or a mucous membrane, accompanied by the disintegration of tissue. Ulcers can result in complete loss of the epidermis and often portions of the dermis and even subcutaneous fat. Ulcers are most common on the skin of the lower extremities and in the gastrointestinal tract. An ulcer that appears on the skin is often visible as an inflamed tissue with an area of reddened skin. A skin ulcer is often visible in the event of exposure to heat or cold, irritation, or a problem with blood circulation.

They can also be caused due to a lack of mobility, which causes prolonged pressure on the tissues. This stress in the blood circulation is transformed into a skin ulcer, commonly known as bedsores or decubitus ulcers. Ulcers often become infected, and pus forms.