Lymphatic capillaries (initial lymphatics)
Source region and uptake · Blind-ended One-way inlet
Blind-ended endothelial tubes whose overlapping cell junctions act as one-way inlet valves, held open by anchoring filaments when interstitial pressure rises. Their permeable wall admits protein, bacteria, single tumour cells and chylomicrons that blood capillaries exclude.
Detail
- Wall
- Overlapping endothelial flaps, no tight junctions, scanty basement membrane
- Held open by
- Anchoring filaments to surrounding collagen
- Opens when
- Interstitial fluid pressure rises
- Absent from
- CNS parenchyma, cornea, epidermis, cartilage, bone marrow
- In the gut
- Lacteals take up long-chain fat as chylomicrons
When it goes wrong
Permeable wall admitting single tumour cells
Lymphatic route of metastasis, arriving first at the sentinel node
Wuchereria bancrofti obstructing lymphatics
Filarial lymphoedema, the commonest cause of lymphoedema worldwide
Practise this structure
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