Јаје

За другу употребу, погледајте чланак Јаје (храна).

Јаја разних птица, рептила, разних хрскавичних риба, сипа и разних лептира и мољаца.

Схема грађе птичјег јајета:
1. љуска јајета
2. спољашња мембрана
3. унутрашња мембрана
4. халаза
5. спољашњи албумен (беланце)
6. средишњи албумен (беланце)
7. вителинска мембрана
8. # бластодерм
10. жуто жуманце
11. бело жуманце
12. унутрашњи албумен (беланце)
13. халаза
14. ваздушна комора
15. кутикула

Јаје представља јајну ћелију животиња, окружену јајним опнама. Код свих животиња изузев неких дупљара, јајне ћелије се „пакују“ у јајне опне пре или након оплођења. Јаје је репродуктивна ћелија женке и након оплодње са мушком полном ћелијом (сперматозоидом), ако се исправно инкубира, развиће се пиле. Током двадесетодневног периода док је ембрион у љусци, садржај у јајету служи као једини извор хране за пиле у развоју. Јаје је једна од најкомплетнијих намирница познатих човеку јер садржи изванредно избалансиран однос протеина, масти, угљених хидрата, минерала и витамина.

Љуска јајета

Јаје је обавијено љуском која је састављена од кречњака. она је веома слаба јер је кречњачки слој веома танак.

Научне класификације

Scientists often classify animal reproduction according to the degree of development that occurs before the new individuals are expelled from the adult body, and by the yolk which the egg provides to nourish the embryo.

Egg size and yolk

Vertebrate eggs can be classified by the relative amount of yolk. Simple eggs with little yolk are called microlecithal, medium-sized eggs with some yolk are called mesolecithal, and large eggs with a large concentrated yolk are called macrolecithal. This classification of eggs is based on the eggs of chordates, though the basic principle extends to the whole animal kingdom.

Microlecithal

Microlecithal eggs from the roundworm Toxocara

Microlecithal eggs from the flatworm Paragonimus westermani

Small eggs with little yolk are called microlecithal. The yolk is evenly distributed, so the cleavage of the egg cell cuts through and divides the egg into cells of fairly similar sizes. In sponges and cnidarians the dividing eggs develop directly into a simple larva, rather like a morula with cilia. In cnidarians, this stage is called the planula, and either develops directly into the adult animals or forms new adult individuals through a process of budding.

Microlecithal eggs require minimal yolk mass. Such eggs are found in flatworms, roundworms, annelids, bivalves, echinoderms, the lancelet and in most marine arthropods. In anatomically simple animals, such as cnidarians and flatworms, the fetal development can be quite short, and even microlecithal eggs can undergo direct development. These small eggs can be produced in large numbers. In animals with high egg mortality, microlecithal eggs are the norm, as in bivalves and marine arthropods. However, the latter are more complex anatomically than e.g. flatworms, and the small microlecithal eggs do not allow full development. Instead, the eggs hatch into larvae, which may be markedly different from the adult animal.

In placental mammals, where the embryo is nourished by the mother throughout the whole fetal period, the egg is reduced in size to essentially a naked egg cell.

Mesolecithal

Frogspawn is mesolecithal.

Mesolecithal eggs have comparatively more yolk than the microlecithal eggs. The yolk is concentrated in one part of the egg (the vegetal pole), with the cell nucleus and most of the cytoplasm in the other (the animal pole). The cell cleavage is uneven, and mainly concentrated in the cytoplasma-rich animal pole.

The larger yolk content of the mesolecithal eggs allows for a longer fetal development. Comparatively anatomically simple animals will be able to go through the full development and leave the egg in a form reminiscent of the adult animal. This is the situation found in hagfish and some snails. Animals with smaller size eggs or more advanced anatomy will still have a distinct larval stage, though the larva will be basically similar to the adult animal, as in lampreys, coelacanth and the salamanders.

Macrolecithal

A baby tortoise begins to emerge "fully developed" from its macrolecithal egg.

Eggs with a large yolk are called macrolecithal. The eggs are usually few in number, and the embryos have enough food to go through full fetal development in most groups. Macrolecithal eggs are only found in selected representatives of two groups: Cephalopods and vertebrates.

Macrolecithal eggs go through a different type of development than other eggs. Due to the large size of the yolk, the cell division can not split up the yolk mass. The fetus instead develops as a plate-like structure on top of the yolk mass, and only envelopes it at a later stage. A portion of the yolk mass is still present as an external or semi-external yolk sac at hatching in many groups. This form of fetal development is common in bony fish, even though their eggs can be quite small. Despite their macrolecithal structure, the small size of the eggs does not allow for direct development, and the eggs hatch to a larval stage ("fry"). In terrestrial animals with macrolecithal eggs, the large volume to surface ratio necessitates structures to aid in transport of oxygen and carbon dioxide, and for storage of waste products so that the embryo does not suffocate or get poisoned from its own waste while inside the egg, see amniote.

In addition to bony fish and cephalopods, macrolecithal eggs are found in cartilaginous fish, reptiles, birds and monotreme mammals. The eggs of the coelacanths can reach a size of 9 cm (3,5 in) in diameter, and the young go through full development while in the uterus, living on the copious yolk.

Egg-laying reproduction

Animals are commonly classified by their manner of reproduction, at the most general level distinguishing egg-laying (Latin. oviparous) from live-bearing (Latin. viviparous).

These classifications are divided into more detail according to the development that occurs before the offspring are expelled from the adult's body. Traditionally:

• Ovuliparity means the female spawns unfertilized eggs (ova), which must then be externally fertilised. Ovuliparity is typical of bony fish, anurans, echinoderms, bivalves and cnidarians. Most aquatic organisms are ovuliparous. The term is derived from the diminutive meaning "little egg".
• Oviparity is where fertilisation occurs internally and so the eggs laid by the female are zygotes (or newly developing embryos), often with important outer tissues added (for example, in a chicken egg, no part outside of the yolk originates with the zygote). Oviparity is typical of birds, reptiles, some cartilaginous fish and most arthropods. Terrestrial organisms are typically oviparous, with egg-casings that resist evaporation of moisture.
• Ovo-viviparity is where the zygote is retained in the adult's body but there are no trophic (feeding) interactions. That is, the embryo still obtains all of its nutrients from inside the egg. Most live-bearing fish, amphibians or reptiles are actually ovoviviparous. Examples include the reptile Anguis fragilis, the sea horse (where zygotes are retained in the male's ventral "marsupium"), and the frogs Rhinoderma darwinii (where the eggs develop in the vocal sac) and Rheobatrachus (where the eggs develop in the stomach).
• Histotrophic viviparity means embryos develop in the female's oviducts but obtain nutrients by consuming other ova, zygotes or sibling embryos (oophagy or adelphophagy). This intra-uterine cannibalism occurs in some sharks and in the black salamander Salamandra atra. Marsupials excrete a "uterine milk" supplementing the nourishment from the yolk sac.
• Hemotrophic viviparity is where nutrients are provided from the female's blood through a designated organ. This most commonly occurs through a placenta, found in most mammals. Similar structures are found in some sharks and in the lizard Pseudomoia pagenstecheri. In some hylid frogs, the embryo is fed by the mother through specialized gills.

The term hemotropic derives from the Latin for blood-feeding, contrasted with histotrophic for tissue-feeding.

Литература

• James, John M.; Zeiger, Robert S.; Lester, Mitchell R.; Fasano, Mary Beth; Gern, James E.; Mansfield, Lyndon E.; Schwartz, Howard J.; Sampson, Hugh A.; Windom, Hugh H.; Machtinger, Steven B.; Lensing, Shelly (1998). „Safe administration of influenza vaccine to patients with egg allergy”. The Journal of Pediatrics. 133 (5): 624—8. PMID 9821418. doi:10.1016/S0022-3476(98)70101-5. 
• Takehiko Yamamoto; Mujo Kim (1996-12-13), Hen eggs, ISBN 9780849340055 
• Gilbertus. Compendium Medicine Gilberti Anglici Tam Morborum Universalium Quam Particularium Nondum Medicis Sed & Cyrurgicis Utilissimum. Lugduni: Impressum per Jacobum Sacconum, expensis Vincentii de Portonariis, 1510.

Спољашње везе

• Elmhurst College, Denaturation Protein
• Exploratorium, Anatomy of an Egg
• „Whale Shark – Cartilaginous Fish”. SeaWorld Parks & Entertainment. Архивирано из оригинала 2014-06-09. г. Приступљено 2014-06-26. 
• McGee, Harold J.; Long, Sharon R.; Briggs, Winslow R. (1984). „Why whip egg whites in copper bowls?”. Nature. 308 (5960): 667—8. Bibcode:1984Natur.308..667M. S2CID 4372579. doi:10.1038/308667a0. 
• Arnaldo Cantani (2008). Pediatric Allergy, Asthma and Immunology. Berlin: Springer. стр. 710–713. ISBN 978-3-540-20768-9. 
• Dasgupta, Amitava (2019-01-01), Dasgupta, Amitava, ур., „Chapter 2 - Biotin: Pharmacology, Pathophysiology, and Assessment of Biotin Status”, Biotin and Other Interferences in Immunoassays (на језику: енглески), Elsevier, стр. 17—35, ISBN 978-0-12-816429-7, Приступљено 2020-08-27