Key Takeaways. Key Points Sweat glands are located deep within the skin and primarily regulate temperature. The two main types of sweat glands are eccrine sweat glands and apocrine sweat glands. Eccrine sweat glands are smaller sweat glands. They are coiled tubular glands that discharge their secretions directly onto the surface of the skin. Apocrine sweat glands are coiled tubular glands that discharge in the canals of hair follicles.
The sweat produced may be acted upon by bacteria, causing a noticeable odor. As pointed out by Kohrt et al. Furthermore, while in extreme circumstances excess mineral loss cannot be ruled out as a contributing factor to suboptimal trace mineral status [ ], for most athletes the main routes of loss are likely through other avenues such as urine or the gastrointestinal tract [ , , ]. Taken together, micronutrient supplementation does not seem to be necessary on the basis of sweat excretion during physical activity, provided that dietary intakes are normal [ ].
The sweat glands are often compared to the nephrons of the kidneys, whose main function, among others, is to conserve the vital constituents of the body [ ]. Indeed, sweat glands share some similarities with the renal system; as eccrine glands have mechanisms to conserve Na, Cl, and bicarbonate losses in sweat as discussed in detail in the Mechanisms of secretion and reabsorption section above. For example, in response to aldosterone, sweat glands increase Na reabsorption in the duct leading to a decrease in sweat [Na], albeit with a greater time lag than that of the kidneys.
These adjustments are mediated through changes in renal water reabsorption in response to arginine vasopressin AVP concentrations in the plasma [ ]. With hyperosmotic hypovolemia, AVP binds to vasopressin type 2 receptors of the distal tubule and collecting duct of the kidneys, stimulating aquaporin transport of water. It has been suggested that AVP might facilitate eccrine gland water reabsorption in a similar manner, resulting in attenuated sweating rates and more concentrated sweat as a consequence of water removal from the primary fluid along the duct [ — ].
However, the majority of studies have concluded that neither administration of AVP e. These studies also reported no correlation between plasma AVP concentrations and sweating rate or sweat [Na] [ , , ]. Moreover, one study showed that pharmacological manipulation of vasopressin type 2 receptors with an agonist desmopressin or antagonist tolvaptan prior to exercise had no effect on sweat [Na] [ ]. These results may be explained in part by the relatively sparse ductal membrane expression of aquaporin-5 compared with the secretory coil [ ].
Taken together it appears that AVP does not regulate water loss via the sweat glands as it does in the kidneys; and the sweat duct does not play an important role in water conservation during exercise-heat stress [ , , , ]. Additionally, a recent study suggests that intradermal administration of atrial natriuretic peptide, a cardiac hormone that promotes urinary excretion of sodium and water, has no effect on sweating rate in young adults nor does it affect sweating in response to muscarinic receptor activation [ ].
The notion that sweating is a means to accelerate the elimination of persistent environmental contaminants from the human body has been around for many years [ , ]. Detoxification methods include several hours per day of sauna bathing to stimulate excessive sweating, resulting supposedly in purification of the body and release of toxins from the blood. Some proponents of this method claim that increasing sweating via exercise or heat stress sauna is an effective clinical tool to protect against or overcome illness and disease [ — ].
Others suggest that physical activity leads to better health outcomes as a result of accelerated toxin elimination via thermal sweating [ , ]. As attractive as this idea sounds, there is little if any evidence to date that supports these claims [ , ]. In a series of studies, Genuis et al. The overall finding of these studies was that many chemicals, including persistent organic pollutants, heavy metals, bisphenol A BPA , and phthalate are excreted in sweat.
Such reports [ , , ] have led some to hypothesize that these chemicals are perhaps preferentially excreted in sweat to reduce the body burden. However there are several important methodological limitations to consider when measuring environmental toxicants in sweat. First, many of these studies used sweat collection methods that are susceptible to surface contamination and sweat evaporation, which would artificially increase the concentration of toxicants measured in sweat samples.
For instance, in most of these studies [ — , — ], sweat was collected by the subjects on their own uncontrolled, unsupervised , from any site on their body, by scraping sweat from the skin surface with a stainless steel spatula into a glass jar. With these methods, it is probable that sweat samples were tainted with sebum secretions.
Scraping methods increase the likelihood of skin surface epidermal cells contamination because scraped sweat contains x more lipid than clean sweat [ ]; potentially explaining the high concentrations of some the of lipophilic toxicants in sweat. Furthermore, the method of sweat stimulation exercise, sauna and timing with respect to how long sweating had commenced before collection were not controlled [ — , — ]. Other studies [ , ] used the arm bag method which is also susceptible to skin surface contamination.
As previously discussed the epidermis contains many contaminants, including heavy metals measured in these studies arsenic and lead [ , ]. When using these methods Genuis et al. Furthermore, BPA was detected in the sweat of 16 of the 20 subjects, but only two of the 20 subjects had BPA in their serum.
In another study, PCB 52 concentration was higher in sweat than blood and urine [ ]. Given that interstitial fluid is the precursor to primary sweat secretion it is unlikely that the BPA or PCB 52 collected at the skin surface in these studies can be attributed to eccrine sweat if the chemical is absent in the blood. Instead the chemicals could have originated from sebum secretions or epidermal cell contamination.
One study lends support for this line of thinking: Porucznik et al. The primary avenue for heavy metals excretion, based on tracer studies, is fecal output [ ]. Meanwhile, there are no known mechanisms by which the sweat glands would preferentially secrete concentrate BPA, persistent organic pollutants, and trace metals to facilitate transport out of the body.
Thus direct evidence for sweating as an effective detoxification method is lacking. Still, future well-controlled studies designed to collect clean eccrine sweat are needed to clarify or refute any potential role of sweating as a therapeutic tool to eliminate toxins from the body. While therapeutic health benefits mostly subjective measures from detoxification protocols in some patient populations have been documented, it is important to note that sauna is only one component of a holistic intervention [ ].
Most protocols also include several weeks of strict changes in diet, exercise, and sleep and therefore it is not possible to attribute any benefit solely to sauna therapy [ , , — ]. The efficacy of lower rates of sweat loss, more realistic to the context of everyday life, is unknown [ ]. In fact, increased sweating is often considered a hangover symptom and is part of the Alcohol Hangover Severity Scale used as the standard in alcohol hangover research [ ]. Furthermore, it is commonly believed that an effective cure for hangovers after heavy drinking is to stimulate sweating via exercise or sauna bathing to accelerate recovery from alcohol intoxication.
However, the evidence to date does not support these ideas; not to mention there are significant health concerns with sauna bathing during alcohol hangover [ ]. Interestingly though, perceived sweating was not significantly different between the hangover and control groups in this naturalistic study, while all other individual symptoms successfully differentiated between the two conditions [ ].
Furthermore, alcohol intake has been found to have no or minimal impact on sweating rate in laboratory intervention studies [ , — ]. For instance, two separate studies found no differences in regional sweating rate chest or upper arm in response to hot water immersion [ ] or exercise-heat stress [ ] after alcohol ingestion that lead to 0.
However, the elevated sudomotor response was transient, as sweating rate decreased after 30 min and became even with the water trial by 40 min into heating [ ]. In addition, differences in sweating rates were very low up to 0. It does seem that sweat ethanol concentration increases with ethanol ingestion and rises linearly with increases in blood alcohol concentration. For example, Buono et al. This nearly identical ethanol concentration between blood and sweat supports the idea that sweat ethanol originates from the interstitial fluid and its concentration is not significantly altered during transport through the duct onto the skin surface; which is counter to the suggestion that the sweat glands have homeostatic mechanisms to detoxify the blood via concentrating mechanisms.
Moreover, the main avenue of ethanol elimination from the body is known to be via oxidation by alcohol dehydrogenase and aldehyde dehydrogenase eventually breaking ethanol down to acetyl CoA, all of which occurs in the liver. Taken together the available evidence suggests that sweating likely plays a very small role in alcohol detoxification or hangover cures.
Another important function of the kidneys is excretion of metabolic and dietary waste products. Since some waste products appear in sweat the eccrine glands are also thought of as an excretory organ. For example, sweat contains urea, the major nitrogen-containing metabolic product of protein catabolism. According to Sato [ 15 ], urea readily crosses the eccrine glandular wall and cell membrane and therefore concentrations of urea in sweat are expected to be about the same as that of the plasma.
Some studies report very high urea concentrations in sweat [ — ], up to 50x that of serum [ ], and suggest that this is evidence for a selective transport mechanism across the sweat gland, especially in patients with kidney damage, to clear the blood of high urea concentrations [ ].
However, many of these studies used methods susceptible to sample evaporation collection of sweat drippage [ , ] or surface contamination sweat collected at onset of exercise [ ], which can lead to artificial increases in sweat urea concentrations see Table 2.
Other studies have shown that uric acid and creatinine excretion via sweat is insignificant compared with elimination rates through the kidneys [ , ].
Taken together, there is limited evidence that the sweat glands excretory function makes a substantial contribution to homeostasis [ , ]. As shown in Table 6 , certain medical conditions and medications can impact sweating rate and sweat composition. As discussed in the Thermoregulation section above, evaporation of sweat is crucial for temperature regulation in warm conditions and this is evident in patients suffering from anhidroses.
In particular, heat intolerance is well documented in patients with anhidrotic ectodermal dysplasia, a genetic condition resulting in a paucity of sweat glands over the entire body surface [ 3 , 15 ].
Other conditions associated with reduced sweating include burns and skin grafting [ — ], sunburn [ ], miliaria rubra [ , ], and atopic dermatitis [ , , ], as well as medications that interfere with neural sudomotor mechanisms e.
Hyperhidrosis, where sweating occurs in excess of thermoregulatory demands, can occur with primary etiology [ 3 , 29 ] or secondary to physiologic condition fever, pregnancy, menopause , pathology malignancy, endocrine, metabolic, or psychiatric disorder , or medication cholinesterase inhibitors, SSRIs, opioids [ 3 , — ].
The reader is referred to the supporting references in Table 6 for more details on each of the conditions and medications that alter sweat gland function. This paper discussed sweat gland physiology and the state of the evidence regarding various roles of sweating and sweat composition in human health. Based on this review of the literature, the following conclusions were drawn:. It is well established that eccrine sweat glands have a tremendous capacity to secrete sweat for the liberation of heat during exercise and exposure to hot environments.
They also have the capacity to enhance sweating rate with heat acclimation for improved heat tolerance. Eccrine sweat glands reabsorb NaCl and bicarbonate to minimize disruptions to whole-body electrolyte balance and acid—base balance, respectively. NaCl reabsorption by the sweat glands improves with whole-body NaCl deficits heat acclimation, dietary restriction , but the response is somewhat delayed 1—3 days compared with that of the kidneys within 1—3 h.
Individuals with salty sweat e. Eccrine gland mechanisms for secretion and reabsorption of other sweat solutes are poorly understood; nonetheless, sweating-induced deficiencies appear to be of minimal risk for trace minerals e. Ca and Fe , vitamins, and other constituents. Eccrine sweating may play a role in skin hydration and microbial defense, but additional research is required.
The role of the sweat glands in eliminating waste products and toxicants from the body seems to be minor compared with other avenues of breakdown liver and excretion kidneys and gastrointestinal tract. Evidence for a selective mechanism to excrete metabolic and dietary waste products and toxicants via the sweat glands is lacking. That is, sweat glands do not appear to adapt in any way to increase excretion rates of these substances either via concentrating sweat or increasing overall sweating rate as the kidneys do in contributing to the regulation of blood concentrations.
Unlike the renal system, sweat glands do not appear to conserve water loss or concentrate sweat fluid through AVP-mediated water reabsorption. Studies suggesting a larger role of sweat glands in clearing waste products or toxicants from the body e. The utility of sweat composition as a biomarker for human physiology is currently limited; more research is needed to determine potential relations between sweat and blood solute concentrations. Lindsay B. Lindsay has been conducting sports nutrition, hydration, and sweat studies for the GSSI research program since The views expressed in this article are those of the authors and do not necessarily reflect the position or policy of PepsiCo, Inc.
National Center for Biotechnology Information , U. Journal List Temperature Austin v. Temperature Austin. Published online Jul Author information Article notes Copyright and License information Disclaimer. Baker moc. This article has been cited by other articles in PMC. Types of sweat glands The purpose of this section is to compare and contrast the three main types of sweat glands: eccrine, apocrine, and apoeccrine [ 5 , 6 ], which are illustrated in Figure 1.
Open in a separate window. Figure 1. Comparison of the apocrine, eccrine, and apoeccrine glands in the axilla. Eccrine sweat glands Eccrine glands were the first type of sweat gland discovered; as they were initially described in by Purkinje and Wendt and in by Breschet and Roussel de Vouzzeme, but were not named eccrine glands until almost years later by Schiefferdecker [ 11 ]. Apocrine sweat glands The apocrine gland is a second type of sweat gland, which was first recognized by Krause in and later named by Schiefferdecker in [ 20 , 21 ].
Apoeccrine sweat glands A third type of sweat gland, only recently described by Sato et al. Sebaceous glands Sebaceous glands are not a type of sweat gland but worth mentioning here since their secretions can impact the composition of sweat collected at the skin surface [ 25 ]. Structure and function of eccrine sweat glands Anatomy The anatomical structure of the eccrine sweat gland, illustrated in Figure 2 , consists of a secretory coil and duct made up of a simple tubular epithelium.
Figure 2. Mechanisms of secretion and reabsorption Secretion The basic mechanism by which secretion of primary sweat occurs in the clear cells, according to the Na-K-2Cl cotransport model, is illustrated in Figure 2 c. Ion reabsorption Figure 2 d shows the mechanism of ion reabsorption according to the modified Ussing leak-pump model. Sweat gland metabolism Transport of Na across cellular membranes is an active process, thus sweat secretion in the clear cells and Na reabsorption in the duct require ATP.
Control of eccrine sweating Eccrine sweat glands primarily respond to thermal stimuli; particularly increased body core temperature [ 40 ], but skin temperature and associated increases in skin blood flow also play a role [ 9 , 46 — 49 ]. Figure 3. Modifiers of eccrine sweating Several intra- and interindividual factors can modify the control of sweating [ 60 ], some of which are shown in Figure 3.
Table 1. Host and environmental factors that modify sweat gland function. Limited data on sweat composition. Sudomotor changes due to gland hypertrophy, increased cholinergic and aldosterone sensitivity, and decreased threshold for sweat onset see Figure 3. Aerobic training Chronic Increase in WBSR and RSR because of increased cholinergic sensitivity and decreased threshold for sweat onset [ 66 — 69 ] see Figure 3 ; limited data for sweat composition Sex Chronic Higher WBSR and RSR in men because of greater cholinergic responsiveness see Figure 3 and maximal sweating rate, but only at high evaporative requirements for heat balance [ 83 , 99 — ]; otherwise higher WBSR often observed in men are related to higher body mass and metabolic heat production, rather than sex per se [ — ].
Minimal differences in sweat [Na], [Cl], and [lactate] due to sex per se [ , , , — ]; limited data on other constituents Menstrual cycle Cyclical No effect on WBSR [ , — ], but lower RSR at a given body core temperature increased threshold and decreased slope during luteal phase [ — ]; no effect on sweat [Na], [Cl], or [K] [ ] Circadian Rhythm Cyclical Increased sweating threshold in the afternoon — h vs.
Limited data on sweat composition, but there seems to be no impact of age per se on sweat [Na] [ 67 ]. Table 2. Common methodological issues. Begin sweat collection after onset of sweating, i. When sealed during storage, no change in sweat [Na], [Cl], or [K] when refrigerated, frozen, or at room temperature for 7 days [ ]. Seal e. RSR: regional sweating rate.
Table 3. Sweat micronutrients: Mechanisms and methodological considerations. Primary sweat is nearly isotonic with blood plasma [ 6 , 8 , ]; Mixed results with respect to relation between flow rate and sweat [K] [ 6 , , , ]; thought to be secreted during sweat passage along the duct, but mechanism unknown [ — ] Often overestimated by up to x with arm bag technique due to surface contamination [ , ] Calcium b 0.
Table 4. Inverse relation between sweating rate and sweat lactate concentration dilution effect , but direct relation between sweating rate and lactate excretion rate [ — ]. Natural skin moisturizer [ 15 , ] Excretion of metabolic waste — not enough evidence [ ] Concentration varies with changes in sweating rate.
Readily crosses glandular wall and cell membrane and therefore concentrations expected to be same as or slightly higher than plasma [ 15 ]. However, measured concentrations are often significantly higher in sweat than plasma [ — ]; possibly because synthesis of urea by the gland [ 6 ] or surface contamination issues. Natural skin moisturizer [ 15 ] Excretion of metabolic waste — not enough evidence [ ] Concentration changes with variation in sweating rate [ 6 ].
Primarily derived from plasma NH 3 by nonionic passive diffusion of NH 3 to acidic ductal sweat and ionic trapping of NH 4 [ 6 , 15 ]. HCO 3 reabsorption is inversely related to sweating rate i. Thus final sweat pH is lower more acidic at lower sweating rate [ 5 , 8 , 37 , ] Dictates pH of sweat [ 5 , 8 ] Concentration varies with changes in sweating rate [ 37 , ] Glucose 0.
Plasma glucose is the primary energy source for eccrine sweat gland secretory activity [ 6 , 41 ]. NA specific to its presence in sweat Possible skin surface contamination from residual glucose in sweat ducts Heavy Metals e. IgG, IgA and Antimicrobial peptides e. Potential for contamination by epidermal protein [ 6 ]. Cytokines e. Concentrations increase with increasing sweating rate [ ].
NA specific to its presence in sweat Skin surface contamination, both of epidermal origin and residual cytokines in the sweat gland lumen [ ] Amino acids e. Skin maintenance and protection via desquamation of horny layer, hydrolysis of debris in the ductal lumen, allergen inhibition [ ] Skin surface contamination, both of epidermal origin [ ] and residual proteolytic enzymes in the sweat gland lumen [ ] Persistent Organic Pollutants e. Persistent organic pollutants are lipophilic and thus may appear on skin surface through sebum secretions [ ].
BPA, phthalate, polybrominated diphenyl ethers a NA No [ , , ] Concentrations are often significantly higher in sweat than plasma [ , , ], but no known mechanisms for preferential secretion. Table 5. Formula diet: Upper arm: 47 vs. Figure 4. Eccrine sweat composition Methodological considerations In science, the accuracy and reliability of study methodology are critical to interpret results and draw conclusions about the impact of an intervention or other factor on the outcome measure of interest.
Overview of sweat composition Sweat is a very complex aqueous mixture of chemicals. Sodium chloride It is well established that sweat [Na] and [Cl] can vary considerably among individuals. Figure 5.
Effect of sweat flow rate Sodium chloride Sweat flow rate is another important factor determining final sweat [Na] and [Cl] and of other aspects of sweat composition. Figure 6. Figure 7. Figure 8. Figure 9. Bicarbonate, pH, and lactate In addition to Na and Cl conservation, another important function of the sweat gland is reabsorption of bicarbonate for the maintenance of acid-base balance of the blood [ 8 ].
Sweat composition as a biomarker There has been considerable interest recently in the use of sweat as a non-invasive alternative to blood analysis to provide insights to human physiology, health, and performance. Skin health Eccrine sweat is thought to play a role in epidermal barrier homeostasis through its delivery of water, natural moisturizing factors, and antimicrobial peptides to the skin surface.
Role in micronutrient balance Sweat gland adjustments in response to deficiency or excess Heat acclimation Sodium chloride The changes in sweat [Na] and [Cl] during heat acclimation have been well established and reviewed in previous papers [ , ] and therefore will not be comprehensively discussed here. Trace minerals A common question on the topic of heat acclimation is whether or not electrolytes or minerals other than NaCl are conserved.
Diet Sodium chloride It is a common perception that Na ingestion influences sweat [Na] or the rate of sweat Na excretion.
Trace minerals Several studies have investigated the hypothesis that dietary intake of trace minerals and vitamins influences sweat composition. Sweating-induced deficiencies Sodium chloride Of all the substances lost in sweat, Na and Cl are lost in the highest concentrations.
Trace minerals and vitamins There have been some suggestions that athletes may require dietary supplementation of certain trace minerals due in part to excessive losses in sweat.
Comparison of sweat gland and kidney function Water conservation and excretion The sweat glands are often compared to the nephrons of the kidneys, whose main function, among others, is to conserve the vital constituents of the body [ ]. Excretion of toxicants The notion that sweating is a means to accelerate the elimination of persistent environmental contaminants from the human body has been around for many years [ , ].
Excretion of metabolic waste Another important function of the kidneys is excretion of metabolic and dietary waste products. Altered sweat gland function from conditions and medications As shown in Table 6 , certain medical conditions and medications can impact sweating rate and sweat composition. Table 6. Conditions and medications that alter sweat gland function. Etiology involves neurogenic overactivity of otherwise normal sweat glands [ 3 , 29 ]; associated with genetic predisposition [ , ].
Tattoos Chronic Reduced sweating rate and higher sweat [Na] in response to pharmacologically-induced local sweating than non-tattooed skin; unknown etiology [ — ]. More research involving exercise or heat-induced whole body sweating is needed. Conclusions This paper discussed sweat gland physiology and the state of the evidence regarding various roles of sweating and sweat composition in human health.
Based on this review of the literature, the following conclusions were drawn: It is well established that eccrine sweat glands have a tremendous capacity to secrete sweat for the liberation of heat during exercise and exposure to hot environments.
Fluid needs for training, competition, and recovery in track-and-field athletes. Fluid balance, hydration, and athletic performance. Biology of sweat glands and their disorders. Disorders of sweat gland function. J Am Acad Dermatol. Encapsulated environment. Compr Physiol. The physiology and pharmacology of the eccrine sweat gland In: Goldsmith L, editor. Biochemistry and physiology of the skin. New York: Oxford University Press; The physiology, pharmacology, and biochemistry of the eccrine sweat gland.
Rev Physiol Biochem Pharmacol. Sweating: its composition and effects on body fluids. Ann N Y Acad Sci. J Lab Clin Med. Exercise, heat, and thermoregulation. Eccrine sweat gland disorders. The structure and function of skin. The sweat glands. Biol Rev. Human perspiration. Springfield IL : Charles C. Thomas Publisher; Variations in secretory activity of human sweat glands.
Normal sweat gland function. Regional variations in transepidermal water loss, eccrine sweat gland density, sweat secretion rates and electrolyte composition in resting and exercising humans.
Extrem Physiol Med. Distribution of heat-activated sweat glands in obese and lean men and women. Hum Biol. Functional and morphological changes in the eccrine sweat gland with heat acclimation.
J Appl Physiol Regional and individual variations in the function of the human eccrine sweat gland. J Invest Dermatol. Electron microscopy of human apocrine sweat glands. Apocrine sweat glands In: Goldsmith LA, editor. Morphology and development of an apoeccrine sweat gland in human axillae. Am J Physiol. Sweat secretion by human axillary apoeccrine sweat gland in vitro. Working up a good sweat - the challenges of standardising sweat collection for metabolomics analysis.
Clin Biochem Rev. Why do we have apocrine and sebaceous glands? J R Soc Med. Sebaceous glands In: Goldsmith LA, editor. Axillary hyperhidrosis: eccrine or apocrine?
Clin Exp Dermatol. Apocrine glands in health and disorder. Int J Dermatol. Immunolocalization and translocation of aquaporin-5 water channel in sweat glands. J Dermatol Sci. Functional requirement of aquaporin-5 in plasma membranes of sweat glands. Biomed Res Int. Effects of some ion transport inhibitors on secretion and reabsorption in intact and perfused single human sweat glands. Pflugers Arch. Rapid regulation of electrolyte absorption in sweat duct. J Membr Biol.
Hydrogen ion and electrolyte excretion of the single human sweat gland. The effect of intracutaneous d-aldosterone and hydrocortisone on human eccrine sweat gland function. Sodium secretion and reabsorption in the human eccrine sweat gland. These are only found in the axillae, breast, and pubic and perineal regions.
They are similar to apocrine sweat glands, but open out onto the upper regions of hair follicles, like sebacous glands. They only secrete after puberty. They produce a cloudy secretion, which starts to smell if bacteria react with it.
So, you need to wash, frequently! Sebaceous Glands This diagram shows the main features of a hair, and its associated sweat gland. Apocrine Sweat Glands. Integumentary System. Search for:. Accessory Structures of the Skin. Learning Objective Classify eccrine and apocrine sweat glands. Key Takeaways Key Points Sweat glands are located deep within the skin and primarily regulate temperature.
The two main types of sweat glands are eccrine sweat glands and apocrine sweat glands. Eccrine sweat glands are smaller sweat glands. They are coiled tubular glands that discharge their secretions directly onto the surface of the skin.
Apocrine sweat glands are coiled tubular glands that discharge in the canals of hair follicles. The sweat produced may be acted upon by bacteria, causing a noticeable odor. Key Terms eccrine gland : The major sweat glands of the human body, found in virtually all skin, produce a clear, odorless substance, consisting primarily of water and NaCl. Learning Objective Describe the location and function of sebaeous glands. Key Takeaways Key Points Sebaceous glands are located throughout the skin except in the palms of the hands and soles of the feet.
Sebum is an oily substance composed of fat lipids and the debris of dead fat-producing cells. Sebaceous glands are classified as holocrine glands. Key Terms sebum : A thick oily substance, secreted by the sebaceous glands of the skin, that consists of fat and cellular debris. Learning Objective Describe the structure of fingernails. Key Takeaways Key Points The nail bed contains the blood vessels, nerves, and melanocytes or melanin-producing cells. The eponychium, or cuticle, is situated between the skin of the finger and the nail plate.
It fuses these structures together and provides a waterproof barrier. Deformity or disease of the nails is referred to as onychosis. There are many diseases that can occur with the fingernails and toenails. The most common of these diseases are ingrown nails and fungal infections. Ingrown nails, also known as onychocryptosis, can affect either the fingers or the toes. In this condition, the nail cuts into one or both sides of the nail bed, resulting in inflammation and possibly infection. Key Term keratin : A protein that makes up hair and nails.
Learning Objective Describe the characteristics of body hair. Key Takeaways Key Points Hair primarily serves for protection, warmth, and sensation. Human hair is made of keratin.
0コメント