Acid mantle
BiologicalProcessThe dynamically maintained acidic pH environment of the stratum corneum. Controls ceramide processing, desquamation timing, antimicrobial defence, and microbiome composition simultaneously.
Biological Process
39 entities in this category
Explore the Science of Biological Processes
-
-
AMP-activated protein kinase
BiologicalProcessThe cell's master energy sensor: a heterotrimeric kinase that detects rising AMP:ATP ratios and systematically switches metabolism from anabolic to catabolic programmes.
-
Anagen
BiologicalProcessActive hair growth phase lasting 2-7 years; normally 85-90% of your follicles are in this growth-producing state.
-
Beta oxidation
BiologicalProcessThe mitochondrial pathway that breaks down fatty acids into acetyl‑CoA, increasing acetyl‑CoA/CoA ratios that suppress PDH and shift fuel use toward fat.
-
Blood sugar and skin
BiologicalProcessThe pattern of recurrent postprandial glucose spikes, prolonged hyperglycaemia, and insulin dysregulation that characterises dietary glycaemic load excess and insulin resistance.
-
Caloric restriction
BiologicalProcessA sustained energy deficit in which caloric intake falls below the body's metabolic requirements. The body responds through conserved survival mechanisms.
-
Catagen
BiologicalProcessThe transition phase of the hair cycle, lasting two to three weeks, during which the follicle's inferior segment undergoes controlled apoptotic regression.
-
Cellular senescence
BiologicalProcessProtective when transient and clearable; damaging when accumulated. UV drives both stress-induced senescence in fibroblasts and impairs the immune surveillance that clears senescent cells.
-
Circadian rhythm
BiologicalProcessThe endogenous 24-hour biological programme that coordinates physiological timing across virtually every organ, tissue, and cell type.
-
Desquamation
BiologicalProcessThe pH-regulated enzymatic programme that sheds corneocytes from the stratum corneum surface at a rate matched exactly to keratinocyte production from below.
-
Epidermal calcium gradient
BiologicalProcessThe depth-stratified calcium concentration system that coordinates keratinocyte proliferation, terminal differentiation, lamellar body secretion, and cornified envelope formation in epidermal layers.
-
Ghrelin rebound
BiologicalProcessPhenomenon where hunger hormone levels spike after stopping GLP-1 medications, sometimes exceeding pre-treatment levels.
-
GLP-1 medication discontinuation
BiologicalProcessStopping GLP-1 medication (tirzepatide or semaglutide), which typically leads to appetite signal changes and potential weight regain.
-
Glycation
BiologicalProcessNon‑enzymatic binding of sugars to proteins, forming AGEs that accumulate, cross‑link structural proteins, and drive inflammatory and oxidative damage via RAGE.
-
Glycation-related skin changes
BiologicalProcessSkin dullness, yellowing, stiffness, and slowed repair caused by long‑term AGE buildup, producing a pattern distinct from chronological ageing or UV damage.
-
Gut microbiota
BiologicalProcessThe community of gut microorganisms that modulates immune signalling, inflammation, and microbial metabolites with downstream effects on skin barrier function and disease risk.
-
Gut-skin axis
BiologicalProcessThe bidirectional communication system linking gut microbiota, immune signalling, and microbial metabolites to skin inflammation, barrier function, and disease susceptibility.
-
Hallmarks of ageing
BiologicalProcessA framework of twelve interconnected biological processes - organised into Primary, Antagonistic, and Integrative tiers - that collectively produce the structural decline of ageing tissue.
-
High sugar and processed food intake
BiologicalProcessDietary pattern of elevated sugar and processed food intake that leads to increased blood glucose and potential skin effects.
-
Hypothalamic–pituitary–adrenal axis
BiologicalProcessThe body’s central stress‑response system, driving CRH→ACTH→cortisol signalling systemically and via a parallel cutaneous HPA axis that regulates skin immunity, barrier function, and repair.
-
Ileal brake
BiologicalProcessThe ileal brake is a physiological feedback mechanism by which unabsorbed nutrients in the small intestine triggers the release of satiety hormones that suppress appetite.
-
Inflammageing
BiologicalProcessChronic low-grade sterile inflammation accumulating with age through senescence, cGAS-STING, and NF-κB amplification — impairing tissue repair and driving structural skin ageing.
-
Insulin signalling
BiologicalProcessThe PI3K–AKT signalling pathway triggered by insulin receptor activation that drives glucose uptake, suppresses hepatic glucose output, and restrains adipose lipolysis.
-
Keratinocyte differentiation
BiologicalProcessThe coordinated, one-way molecular programme by which a basal keratinocyte progresses through the epidermal layers to produce the structural and biochemical components of the skin barrier.
-
Lamellar body secretion
BiologicalProcessThe calcium-triggered exocytosis event at the stratum granulosum–stratum corneum interface that delivers ceramide precursors, enzymes, and antimicrobial peptides into the extracellular space.
-
Lipid synthesis
BiologicalProcessThe biological process by which skin cells produce ceramides, cholesterol, and fatty acids - the structural lipid building blocks of the stratum corneum's protective barrier.
-
Metabolic adaptation
BiologicalProcessMetabolic adaptation is the physiological reduction in resting energy expenditure that exceeds what would be predicted from changes in body weight and composition alone during caloric restriction.
-
Metabolic chronodisruption
BiologicalProcessThe process by which metabolic inflexibility depletes cellular NAD⁺, stalling SIRT1 deacetylase activity and progressively dampening the molecular circadian clock.
-
Oestrogen decline
BiologicalProcessThe progressive reduction in oestrogen that begins in the early 40s and accelerates through perimenopause into menopause, driving simultaneous changes across the dermis, epidermis, and skin barrier.
-
Oxidative phosphorylation
BiologicalProcessOxidative phosphorylation generates the bulk of cellular ATP in mitochondria, coupling oxygen use to energy production while also producing ROS, a process central to tissue function and ageing.