Respiratory System - Diaphragm

From Embryology
Revision as of 18:53, 11 December 2012 by Z8600021 (talk | contribs) (→‎References)
Embryology - 28 Mar 2024    Facebook link Pinterest link Twitter link  Expand to Translate  
Google Translate - select your language from the list shown below (this will open a new external page)

العربية | català | 中文 | 中國傳統的 | français | Deutsche | עִברִית | हिंदी | bahasa Indonesia | italiano | 日本語 | 한국어 | မြန်မာ | Pilipino | Polskie | português | ਪੰਜਾਬੀ ਦੇ | Română | русский | Español | Swahili | Svensk | ไทย | Türkçe | اردو | ייִדיש | Tiếng Việt    These external translations are automated and may not be accurate. (More? About Translations)

Introduction

Historic diagram showing the position of the diaphragm in human embryos of different stages.
Adult Diaphragm

The respiratory system does not carry out its physiological function (gas exchange) prenatally and postnatally the lungs continue to grow for another 8+ years. Many other tissues/systems are involved in respiratory function: musculoskeletal (ribs and diaphragm) cardiovascular (pulmonary circulation). The musculoskeletal begins functioning prenatally, the cardiovasular pulmonary circulation is activated and altered postnatally.

The diaphragm along with the ribcage are the musculoskeletal structures that regulate lung inflation. The topic of musculoskeletal development is also covered in a separate set of notes (More? Musculoskeletal System Development).

In humans, the muscles of the diaphragm arise from somite level 3 to 5 (C3 to C5), which also corresponds to the levels of segmental nerves providing innervation of the diaphragm.

Failure of complete diaphragm development can lead to a herniation of abdominal components through channels or gaps in the developing diaphragm into the pleural cavity.

In humans, in the third trimester preparatory fetal respiratory movements occur, which are thought to have a number of roles in late respiratory development.

Respiratory Links: respiratory | Science Lecture | Lecture Movie | Med Lecture | Stage 13 | Stage 22 | upper respiratory tract | diaphragm | Histology | Postnatal | respiratory abnormalities | Respiratory Quiz | Respiratory terms | Category:Respiratory
Historic Embryology - Respiratory 
1902 The Nasal Cavities and Olfactory Structures | 1906 Lung | 1912 Upper Respiratory Tract | 1912 Respiratory | 1913 Prenatal and Neonatal Lung | 1914 Phrenic Nerve | 1918 Respiratory images | 1921 Respiratory | 1922 Chick Pulmonary Vessels | 1934 Right Fetal Lung | 1936 Early Human Lung | 1937 Terminal Air Passages | 1938 Human Histology

Diaphragm Components

Diaphragm components.jpg Five elements contribute to the diaphragm.

septum transversum - central tendon

3rd to 5th somite - musculature of diaphragm (More? Somitogenesis)

ventral pleural sac - connective tissue

mesentry of oesophagus - connective tissue around oesophasus and IVC (More? Gastrointestinal Tract Development)

pleuroperitoneal membranes - connective tissue around central tendon

Pleuroperitoneal Fold

Rat pleuro-peritoneal membranes (historic drawing)

The transient pleuroperitoneal fold (PPF) arise from the posterior body wall, and appears in late week 4 (Carnegie stage 13/14, CRL 6mm) and is present until week 6 (Carnegie stage 17, CRL 14mm).[1] After this time it can no longer be separated from the diaphragm. These pair of folds have a triangular shape and abnormalities in their development is related to congenital diaphragmatic hernia (CDH).

Diaphragm Innervation

Gray0804.jpg
Adult Cervical Plexus (phrenic nerve shown lower right)
Innervation of the human diaphragm is by the phrenic nerves, arising from the same segmental levels from which the diaphragm skeletal muscles arise, segmental levels C3 to C5.

The paired phrenic nerves are mixed containing motor neurons for the diaphragm and sensory nerves for other abdominal structures (mediastinum, pleura, liver, gall bladder).

The two adult phrenic nerves differ in their length, and also in their anatomical relations at the upper part of the thorax.

Netrin signaling may be important in early phrenic nerve growth, as knockout mice show incomplete phrenic nerve innervation of the diaphragm.

Other respiratory muscles include the intercostals which are innervated by the intercostal nerves arising from segmental levels T1 to T11.

  • Key aspects of phrenic motoneuron and diaphragm muscle development during the perinatal period.[2]
  • Motor axon guidance of the mammalian trochlear and phrenic nerves: dependence on the netrin receptor Unc5c and modifier loci.[3]

 

Fetal Respiratory Movements

Fetal respiratory movements (FRM) or Fetal breathing movements (FBM) are thought to be regular muscular contrations occurring in the third trimester, preparing the respiratory muscular system for neonatal function and to also have a role in late lung development.

The majority of FBM research has been carried out in fetal sheep.[4]

Hypoxia, decreased oxygen levels, blocks these movements by inhibition of the brain stem respiratory centres.

Hypercapnia, increased carbon dioxide levels, or acid cerebrospinal fluid perfusion can cause an increase in the regularity and depth of breathing.

Hormones also affect fetal breathing movements: inhibitors of prostaglandin synthetase (indomethacin, meclofenamate or aspirin) induce continuous fetal breathing movements, while prostaglandin E2 arrests fetal breathing.

  • The effect of fetal breathing movements on pulmonary blood flow in fetal sheep.[5] "FBM do not increase mean blood flow through the left pulmonary artery; thus, it is unlikely that FBM stimulate lung growth through changes in pulmonary blood flow."
  • Maturation of fetal breathing activity.[6]
  • The central control of fetal breathing and skeletal muscle movements.[7]

Hypercapnia (Greek, hyper = "above" and kapnos = "smoke") or hypercarbia increased carbon dioxide levels.

 

Abnormalities

Human congenital diaphragmatic hernia[8]

Congenital Diaphragmatic Hernia

International Classification of Diseases code Q79.0

Failure of the pleuroperitoneal foramen (foramen of Bochdalek) to close allows viscera into thorax. Intestine, stomach or spleen can enter the pleural cavity, compressing the lung.

Congenital diaphragmatic hernia 01.jpg
Left posterolateral diaphragmatic hernia[9]
  • A - Plain X-ray of the thorax of a newborn with CDH. There are bowel loops into the left hemi-thorax, the mediastinum is displaced to the contralateral side and the space occupied by the lung is reduced.
  • B - small bowel loops can be seen entering the thorax through the orifice.
  • C - seen after reducing the contents of the hernia.
  • D - At autopsy, extreme left lung hypoplasia and less severe right lung hypoplasia were discovered.

Australian national rate (1982-1992) 2.1 - 3.8 /10,000 births.[10]

  • Prenatal detection and outcome of congenital diaphragmatic hernia: a French registry-based study.[11] "501 cases of CDH were identified from a total of 1,835,022 live births (2.7/10 000 live births). The overall prenatal detection rate was 54%."
  • Outcomes of congenital diaphragmatic hernia: a population-based study in Western Australia.[12] "Ninety-two percent of postoperative infants survived beyond 1 year of age, as did 80% of infants who reached the surgical referral center. However, only 52% of live-born infants, 32% of all cases, and 16% of all prenatally diagnosed cases survived. Therefore, the overall mortality rate for this condition remains high, despite increased prenatal detection, transfer to tertiary institutions for delivery, and advances in neonatal care, and is influenced significantly by the rate of prenatal termination. In our study, 33% of all cases of CDH and 49% of prenatally diagnosed fetuses underwent elective termination of pregnancy. This large number of fetal terminations confounds the accurate assessment of the true outcomes of this condition."


Links: Respiratory Abnormalities | Search Pubmed - CDH | Search OMIM - CDH

Adult Diaphragm

Gray0391.jpg
Historic image of adult diaphragm (viewed from beneath)

References

  1. <pubmed>19711422</pubmed>
  2. <pubmed>18403452</pubmed>
  3. <pubmed>16723533</pubmed>
  4. <pubmed>8047386</pubmed>
  5. <pubmed>8047386</pubmed>
  6. <pubmed>8038281</pubmed>
  7. <pubmed>6422029</pubmed>
  8. <pubmed>16483386</pubmed>| Theor Biol Med Model.
  9. <pubmed>22214468</pubmed>| Orphanet J Rare Dis.
  10. P. Lancaster and E. Pedisich Congenital Malformations Australia 1981-1992 ISSN 1321-8352.
  11. <pubmed>17177265</pubmed>
  12. <pubmed>16140678</pubmed>

Reviews

<pubmed></pubmed> <pubmed>22214468</pubmed> <pubmed>18510546</pubmed> <pubmed>18403452</pubmed> <pubmed>16723533</pubmed> <pubmed></pubmed>

Articles

<pubmed>21370493</pubmed>

Search PubMed Now

Search PubMed Now: diaphragm development | phrenic nerve development | fetal respiratory movements | Pubmed - Congenital Diaphragmatic Hernia | OMIM - Congenital Diaphragmatic Hernia

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

Cite this page: Hill, M.A. (2024, March 28) Embryology Respiratory System - Diaphragm. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Respiratory_System_-_Diaphragm

What Links Here?
© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G