View source for Lamina propria

{{Short description|Thin connective tissue layer of mucous membranes}}
{{Infobox anatomy
| Name        = Lamina propria
| Part_of     = [[Mucous membrane|Mucosa]]
| Latin       = lamina propria mucosæ
| Width       = 
| Image      = Oral mucosa.png
| Caption    = The lamina propria, a thin layer of connective tissue, is part of the [[mucous membrane|mucosa]]. Here is an example of the mucosa of the [[mouth]].
| Precursor   = 
| System      = 
| Artery      = 
| Vein        = 
| Nerve       = 
| Lymph       = 
}}
The '''lamina propria''' is a thin layer of [[connective tissue]] that forms part of the moist linings known as mucous membranes or [[mucosae]], which line various tubes in the body, such as the [[respiratory tract]], the [[gastrointestinal tract]], and the [[urogenital tract]].

The lamina propria is a thin layer of [[Loose connective tissue|loose (areolar) connective tissue]], which lies beneath the [[epithelium]], and together with the epithelium and [[basement membrane]] constitutes the [[mucosa]]. As its Latin name indicates, it is a characteristic component of the mucosa, or the mucosa's "own special layer." Thus, the term [[mucosa]] or mucous membrane refers to the combination of the epithelium and the lamina propria.<ref>{{cite book |editor1-first=H. George |editor1-last=Burkitt |editor2-first=Barbara |editor2-last=Young |editor3-first=John W. |editor3-last=Heath |year=1993 |title=Wheater's Functional Histology |publisher=Churchill Livingstone |edition=3rd |isbn=978-0-443-04691-9 |url-access=registration |url=https://archive.org/details/wheatersfunction00hgeo }}{{page needed|date=May 2015}}</ref>

The connective tissue of the lamina propria is loose and rich in cells. The cells of the lamina propria are variable and can include [[fibroblast]]s, [[lymphocyte]]s, [[plasma cell]]s, [[macrophage]]s, [[eosinophil]]ic [[leukocyte]]s, and [[mast cell]]s.<ref>{{cite web |first=Lutz |last=Slomianka |year=2009 |title=Blue Histology-Gastrointestinal Tract |publisher=The University of Western Australia |url=http://www.lab.anhb.uwa.edu.au/mb140/CorePages/GIT/git.htm}}</ref> It provides support and nutrition to the epithelium, as well as the means to bind to the underlying tissue. Irregularities in the connective tissue surface, such as [[Lingual papillae|papilla]]e found in the [[tongue]], increase the area of contact of the lamina propria and the epithelium.<ref>{{cite book |first=Anthony |last=Mescher |year=2009 |title=Junqueira's Basic Histology: Text & Atlas |publisher=McGraw Hill Professional |edition=12th |isbn=978-0-07-171475-4}}{{page needed|date=May 2015}}</ref>

==Structure==
The lamina propria is a loose [[connective tissue]], hence it is not as fibrous as the underlying connective tissue of the submucosa.<ref name="King 2009 Study Guide">{{cite web |first=David |last=King |year=2009 |title=Study Guide: Histology of the Gastrointestinal System |url=http://www.siumed.edu/~dking2/erg/giguide.htm}}</ref>{{self-published inline|date=May 2015}} The connective tissue and architecture of the lamina propria is very compressible and elastic, this can be seen in organs that require expansion such as the bladder.<ref>{{cite journal |doi=10.1080/003655999750042132 |pmid=10573775 |title=Roles of the Lamina Propria and the Detrusor in Tension Transfer during Bladder Filling |journal=Scandinavian Journal of Urology and Nephrology |volume= 33|pages=38–45 |year=1999 |last1=Chang |first1=S. L. |last2=Chung |first2=J. S. |last3=Yeung |first3=M. K. |last4=Howard |first4=P. S. |last5=MacArak |first5=E. J. |issue=201 }}</ref> The collagen in the lamina propria of elastic organs has been shown to play a major role in mechanical function. In the bladder the collagen composition of its lamina propria allows for structure, tensile strength, and compliance, through complex coiling.<ref name=pmid23847015>{{cite journal |doi=10.1002/nau.22465 |pmid=23847015 |title=Lamina propria: The functional center of the bladder? |journal=Neurourology and Urodynamics |volume=33 |issue=1 |pages=9–16 |year=2014 |last1=Andersson |first1=Karl-Erik |last2=McCloskey |first2=Karen D. |doi-access=free }}</ref> It has been suggested that myofibroblasts also reside in the lamina propria of several organs. These cells have characteristics of both smooth muscle and fibroblasts.<ref name=pmid12614258>{{cite journal |doi=10.1046/j.1464-410X.2003.03802.x |pmid=12614258 |title=The role of the human bladder lamina propria myofibroblast |journal=BJU International |volume=91 |issue=1 |pages=89–93 |year=2003 |last1=Wiseman |first1=O.J. |last2=Fowler |first2=C.J. |last3=Landon |first3=D.N. |s2cid=7628206 }}</ref>
    
The lamina propria may also be rich in vascular networks, lymphatic vessels, elastic fibers, and smooth muscle fascicles from the [[muscularis mucosae]]. Afferent and efferent nerve endings can be found in the lamina propria as well.<ref name=pmid23847015/> Immune cells as well as lymphoid tissue, including lymphoid nodules and capillaries, may be present. Smooth muscle fibers may be in the lamina propria, such as in the intestinal villi. It is practically void of fat cells.<ref name="King 2009 Study Guide"/> Lymphatics penetrate the mucosa and lie below the basement membrane of the epithelium, from there they drain the lamina propria.<ref name=pmid9527214>{{cite journal |doi=10.1016/S0003-4975(97)01387-8 |pmid=9527214 |title=Esophageal Carcinoma: Depth of Tumor Invasion is Predictive of Regional Lymph Node Status |journal=The Annals of Thoracic Surgery |volume=65 |issue=3 |pages=787–92 |year=1998 |last1=Rice |first1=Thomas W |last2=Zuccaro |first2=Gregory |last3=Adelstein |first3=David J |last4=Rybicki |first4=Lisa A |last5=Blackstone |first5=Eugene H |last6=Goldblum |first6=John R }}</ref> The fast rate of cell death and regeneration of the epithelium leaves behind many apoptotic cell bodies. These have been found to go into the lamina propria, most of which are inside its macrophages.<ref>{{cite journal |pmid=7706406 |url=http://jcs.biologists.org/cgi/pmidlookup?view=long&pmid=7706406 |year=1994 |last1=Hall |first1=Peter A. |title=Regulation of cell number in the mammalian gastrointestinal tract: The importance of apoptosis |journal=Journal of Cell Science |volume=107 |issue=12 |pages=3569–77 |last2=Coates |first2=Philip J. |last3=Ansari |first3=Bijan |last4=Hopwood |first4=David |doi = 10.1242/jcs.107.12.3569|url-access=subscription }}</ref>

==Function==
===Role in the immune system===
Because the epithelium is often under external stress and is somewhat delicate, the lamina propria hosts many immune cells.<ref name="King 2009 Study Guide"/> In the intestinal tract the immune system must have tolerance to the normal intestinal flora, yet respond to pathogenic microorganisms. Imbalance of this causes inflammation diseases such as inflammatory bowel disease.<ref>{{cite journal |doi=10.1016/j.immuni.2009.06.025 |pmid=19733097 |title=Intestinal Lamina Propria Dendritic Cell Subsets Have Different Origin and Functions |journal=Immunity |volume=31 |issue=3 |pages=502–12 |year=2009 |last1=Varol |first1=Chen |last2=Vallon-Eberhard |first2=Alexandra |author3-link=Eran Elinav |last3=Elinav |first3=Eran |last4=Aychek |first4=Tegest |last5=Shapira |first5=Yami |last6=Luche |first6=Hervé |last7=Fehling |first7=Hans Jörg |last8=Hardt |first8=Wolf-Dietrich |last9=Shakhar |first9=Guy |last10=Jung |first10=Steffen |doi-access=free }}</ref> The lamina propria’s richness in macrophages and lymphoid cells makes it a key place for immune responses to occur. It forms part of the barrier that protects internal tissues from external pathogenic microorganisms, especially from the gastrointestinal tract.<ref>{{Cite journal|last1=Bischoff|first1=Stephan C|last2=Barbara|first2=Giovanni|last3=Buurman|first3=Wim|last4=Ockhuizen|first4=Theo|last5=Schulzke|first5=Jörg-Dieter|last6=Serino|first6=Matteo|last7=Tilg|first7=Herbert|last8=Watson|first8=Alastair|last9=Wells|first9=Jerry M|date=2014-11-18|title=Intestinal permeability – a new target for disease prevention and therapy|journal=BMC Gastroenterology|volume=14|page=189|doi=10.1186/s12876-014-0189-7|issn=1471-230X|pmc=4253991|pmid=25407511 |doi-access=free }}</ref>

==Clinical significance==
Progression of epithelial [[cancer]] often relies on deep and regional [[lymph node]] invasion.<ref>{{cite journal |doi=10.4111/kju.2012.53.5.317 |pmid=22670190 |pmc=3364470 |title=Prognostic Significance of Substaging according to the Depth of Lamina Propria Invasion in Primary T1 Transitional Cell Carcinoma of the Bladder |journal=Korean Journal of Urology |volume=53 |issue=5 |pages=317–23 |year=2012 |last1=Lee |first1=Ji Yong |last2=Joo |first2=Hee Jae |last3=Cho |first3=Dae Sung |last4=Kim |first4=Sun Il |last5=Ahn |first5=Hyun Soo |last6=Kim |first6=Se Joong }}</ref> The lamina propria, being one of the barriers to the submucosa, is an area where epithelial cancer invasion is of significance since lymphatic invasion is an independent predictor of [[Metastasis#Lymph spread|lymph node metastasis]], especially in [[gastric cancer]].<ref>{{cite journal |doi=10.1016/j.humpath.2006.04.014 |pmid=16938525 |title=Evaluation of lymphatic invasion in primary gastric cancer by a new monoclonal antibody, D2-40 |journal=Human Pathology |volume=37 |issue=9 |pages=1193–9 |year=2006 |last1=Yonemura |first1=Yutaka |last2=Endou |first2=Yoshio |last3=Tabachi |first3=Kayoko |last4=Kawamura |first4=Taiichi |last5=Yun |first5=Hyo-Yung |last6=Kameya |first6=Toru |last7=Hayashi |first7=Isamu |last8=Bandou |first8=Etsurou |last9=Sasaki |first9=Takuma |last10=Miura |first10=Masahiro }}</ref> As soon as the tumors breach the basement membrane and reach the lamina propria, they are exposed to lymphatics which may increase the rate of [[metastasis]] and cancer progression. Deeper invasion into the submucosa will increase the exposure to lymphatics.<ref name=pmid9527214/>

Long-standing [[inflammation]] is a risk factor for the development of cancer. The lamina propria macrophages when under much stress release pro-inflammatory signals that may lead to increased probability of developing cancer. An example of this is the overactivation of the [[Interleukin 6|IL-6]]/[[STAT3]] pathway, which has been linked to colitis-associated cancer.<ref>{{cite journal |first1=Satoshi |last1=Matsumoto |first2=Taeko |last2=Hara |first3=Keiichi |last3=Mitsuyama |first4=Mayuko |last4=Yamamoto |first5=Osamu |last5=Tsuruta |first6=Michio |last6=Sata |first7=Jürgen |last7=Scheller |first8=Stefan |last8=Rose-John |first9=Sho-ichi |last9=Kado |first10=Toshihiko |last10=Takada |year=2009 |title=Essential Roles of IL-6 Trans-Signaling in Colonic Epithelial Cells, Induced by the IL-6/Soluble-IL-6 Receptor Derived from Lamina Propria Macrophages, on the Development of Colitis-Associated Premalignant Cancer in a Murine Model |journal=The Journal of Immunology |volume=184 |issue=3 |pages=1543–51 |doi=10.4049/jimmunol.0801217 |pmid=20042582 |doi-access=free }}</ref>

==See also==
* [[Basal lamina]] (part of which is also known as lamina densa)
* [[Myofibroblast]]
* [[Submucosa]]

==References==
{{Reflist}}

==External links==
* {{AnatomyAtlasesMicroscopic|10|198}}
* {{BUHistology|10802loa}} - "Digestive System: Alimentary Canal - esophagus "
* {{BUHistology|03301loa}} - "Connective Tissue: lamina propria; loose connective tissue "
* {{UIUCHistologySubject|272}}
* {{UCDavisOrganology|Digestive/mammal/system1/system3}} - "Mammal, whole system (LM, Low)"
* [https://web.archive.org/web/20051023212054/http://neuromedia.neurobio.ucla.edu/campbell/connective_tissue/wp_images/107%20submucosa%20lamina%20propria.jpg Slide at ucla.edu]

{{Digestive tract}}

{{DEFAULTSORT:Lamina Propria}}
[[Category:Histology]]