[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Blood vessels](https://durgical.com/en/general-pathology/areas/vessels/) › How an atheroma forms: the response-to-injury model step by step # How an atheroma forms: the response-to-injury model step by step - Mechanism An atheroma is a chronic inflammatory healing response to injured endothelium and trapped cholesterol in the artery wall. Updated Nov 12, 2026 ## Key points - First step: endothelial dysfunction, especially where flow is disturbed (branch points, posterior abdominal aorta). - LDL is retained by proteoglycans and modified (oxidised); macrophages take it up through scavenger receptors, not the LDL receptor. - Foam cells are lipid-laden macrophages (and some smooth-muscle cells); they make the fatty streak. - Inflammasome activation by cholesterol crystals releases IL-1 and amplifies inflammation. - Smooth-muscle cells migrate into the intima and make collagen: the fibrous cap. - Laminar flow is protective; disturbed flow at branch points is not. ## What it is Atherosclerosis is best understood as a chronic inflammatory response of the arterial wall to endothelial injury. Injured or dysfunctional endothelium lets LDL enter the intima, where it is retained and oxidised. Monocytes follow, become macrophages and swallow the modified lipid to form foam cells. Cytokines and growth factors from macrophages, T cells and platelets recruit smooth-muscle cells, which build a fibrous cap. Over decades the fatty streak becomes a fibrofatty plaque. ## Structure - Early: fatty streak, flat yellow streaks of foam cells without obstruction; seen even in adolescents. - Later: fibrofatty atheroma (see the plaque page). ## Step by step - Chronic injury (hyperlipidemia, hypertension, smoking, hyperglycemia, disturbed flow) makes the endothelium dysfunctional. - LDL crosses into the intima, binds proteoglycans and is oxidised. - Endothelial adhesion molecules capture monocytes, which enter the intima and become macrophages. - Macrophages engulf oxidised LDL through scavenger receptors and turn into foam cells. - Cholesterol crystals and modified lipids activate the inflammasome; cytokines recruit T cells and more monocytes. - Platelet and macrophage growth factors draw smooth-muscle cells into the intima, where they make collagen. - A fibrous cap covers a lipid core; dying foam cells enlarge the necrotic core and calcium is deposited. ## Clinical notes - Lowering LDL stabilises and can shrink plaques; anti-inflammatory therapy reduces events in some trials, supporting the inflammatory model. ## Memory aid Damaged door, LDL walks in, macrophages overeat, muscle builds a roof: injury, lipid, foam, cap. ## Test yourself Think of the answer, then tap the question to see it. ## Through which receptors do macrophages take up oxidised LDL? Scavenger receptors (such as CD36 and SR-A), which are not down-regulated by cholesterol, so lipid keeps accumulating. ## Which cell builds the fibrous cap? Smooth-muscle cells that migrated from the media into the intima and synthesise collagen. ## Why do plaques favour branch points? Disturbed, non-laminar flow there causes endothelial dysfunction; laminar shear stress is protective. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/general-pathology/how-an-atheroma-forms-the-response-to-injury-model-step-by-step/) [More Pathology questions →](https://durgical.com/en/practice/?f=pathology) ## Elsewhere in DurgiPedia - [LDL (low-density lipoprotein)](https://durgical.com/en/biochemistry/topics/ldl/) - [Lipoprotein metabolism](https://durgical.com/en/biochemistry/topics/lipoprotein-metabolism/) - [Nitric oxide (NO)](https://durgical.com/en/biochemistry/molecules/nitric-oxide/) - [Monocyte and macrophage](https://durgical.com/en/immunology/monocyte-and-macrophage/) - [Cytokines: the table to know](https://durgical.com/en/immunology/cytokines-the-table-to-know/) ## Connections ## Related 5 - [Vessel wall response to injury](https://durgical.com/en/general-pathology/vessel-wall-response-to-injury/) - [Atherosclerotic plaque: stable vs vulnerable](https://durgical.com/en/general-pathology/atherosclerotic-plaque-stable-vs-vulnerable/) - [Atherosclerosis: risk factors](https://durgical.com/en/general-pathology/atherosclerosis-risk-factors/) - [Chronic inflammation: causes, cells and features](https://durgical.com/en/general-pathology/chronic-inflammation-causes-cells-and-features/) - [Intracellular accumulations: cholesterol, proteins, hyaline, glycogen](https://durgical.com/en/general-pathology/intracellular-accumulations-cholesterol-proteins-hyaline-glycogen/) ## Related conditions 5 - [Atherosclerosis and dyslipidaemia](https://durgical.com/en/conditions/atherosclerosis-and-dyslipidaemia/) - [Stable angina](https://durgical.com/en/conditions/stable-angina/) - [Myocardial Infarction (Heart Attack)](https://durgical.com/en/conditions/myocardial-infarction/) - [Ischaemic stroke](https://durgical.com/en/conditions/ischaemic-stroke/) - [Peripheral artery disease](https://durgical.com/en/conditions/peripheral-artery-disease/) [← All of general pathology](https://durgical.com/en/general-pathology/) Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Atherosclerosis: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000171.htm) (MedlinePlus, US National Library of Medicine, 2025); [Familial hypercholesterolemia: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/familial-hypercholesterolemia/) (MedlinePlus, US National Library of Medicine, 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/general-pathology/how-an-atheroma-forms-the-response-to-injury-model-step-by-step/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/how-an-atheroma-forms-the-response-to-injury-model-step-by-step/