A theca refers to any case

Case

-Academia and education:* Campaign for Science and Engineering , a non-profit organization which promotes science and engineering research in the UK* Case analysis, division of a problem into separate cases...

, covering

Covering

-Mathematics:*In topology:** Covering map, a function from one space to another with uniform local neighborhoods** Cover , a system of sets whose union is a given topological space...

, or sheath

Sheath

Sheath may refer to:* Scabbard, a sheath for holding a sword, knife, or other large blade, as well as guns, such as rifles.* The outer covering of a cable* Condom, a kind of contraception* Debye sheath, a layer of a plasma in physics...

.

In botany

Botany

Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...

, the theca of an angiosperm consists a pair of microsporangia

Microsporangia

Microsporangium is a sporangium that produces spores that give rise to male gametophytes. Microsporangia are notable in spikemosses, and a minority of ferns. In Gymnosperms and Angiosperms , the microsporangium produce the microsporocyte, also known as the microspore mother cell, which then creates...

 that are adjacent to each other and share a common area of dehiscence

Dehiscence (botany)

Dehiscence is the opening, at maturity, in a pre-defined way, of a plant structure, such as a fruit, anther, or sporangium, to release its contents. Sometimes this involves the complete detachment of a part. Structures that open in this way are said to be dehiscent...

 called the stomium. Any part of a microsporophyll that bears microsporangia is called an anther. Most anthers are formed on the apex of a filament

Stamen

The stamen is the pollen producing reproductive organ of a flower...

. An anther and its filament together form a typical (or filantherous) stamen

Stamen

The stamen is the pollen producing reproductive organ of a flower...

, part of the male floral

Flower

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

 organ.

The typical anther is bilocular, i.e. it consists of two thecae. Each theca contains two microsporangia, also known as pollen sacs. The microsporangia produce the microspores, which for seed plants are known as pollen

Pollen

Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...

 grains.

If the pollen sacs are not adjacent, or if they open separately, then no thecae are formed. In Lauraceae, for example, the pollen sacs are spaced apart and open independently.

The tissue between the locules and the cells is called the connective

Connective

Connective may be referring to:* Bains::connective* Logical connective* Connective tissue* Discourse connective, in linguistics, a word or phrase like "therefore" or "in other words"....

 and the parenchyma

Parenchyma

Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, f. Greek παρέγχυμα - parenkhuma, "visceral flesh", f. παρεγχεῖν - parenkhein, "to pour in" f. para-, "beside" + en-, "in" + khein, "to pour"...

. Both pollen sacs are separated by the stomium. When the anther is dehiscing, it opens at the stomium.

The outer cells of the theca form the epidermis

Epidermis (botany)

The epidermis is a single-layered group of cells that covers plants' leaves, flowers, roots and stems. It forms a boundary between the plant and the external environment. The epidermis serves several functions, it protects against water loss, regulates gas exchange, secretes metabolic compounds,...

. Below the epidermis, the somatic

Somatic

The term somatic means 'of the body',, relating to the body. In medicine, somatic illness is bodily, not mental, illness. The term is often used in biology to refer to the cells of the body in contrast to the germ line cells which usually give rise to the gametes...

 cells form the tapetum

Tapetum (botany)

The tapetum is a layer of cells that is found within the pollen sac, a nutritive tissue within the sporangium, particularly within the anther. Tapetum is important for the development of pollen grains. The cells are usually bigger and normally have 2 nuclei per cell...

. These support the development of microspore

Microspore

In biology, a microspore is a small spore as contrasted to the larger megaspore.In botany, microspores develop into male gametophytes, whereas megaspores develop into female gametophytes. The combination of megaspores and microspores is found only in heterosporous organisms...

s into mature pollen grains. However, little is known about the underlying genetic mechanisms, which play a role in male sporo- and gametogenesis.

The thecal arrangement of a typical stamen can be as follows:

• Divergent: both thecae in line, and forming an acute angle with the filament
• Transverse (or explanate): both thecae exactly in line, at right angles with the filament
• Oblique: the thecae fixed to each other in an oblique way
• Parallel: the thecae fixed to each other in a parallel way

In biology

Biology

Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

, the theca of follicle

Theca of follicle

The theca folliculi comprise a layer of the ovarian follicles. They appear as the follicles become tertiary follicles.The theca are divided into two layers, the theca interna and the theca externa....

 can also refer to the site of androgen

Androgen

Androgen, also called androgenic hormone or testoid, is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of male characteristics in vertebrates by binding to androgen receptors...

 production in females.

In human embryogenesis

Human embryogenesis

Human embryology is the study of human development during the first eight weeks from gametogenesis pre-conception through fertilization up to and including the 8th week after implantation of the zygote in the uterus...

 the theca cells form a corpus luteum

Corpus luteum

The corpus luteum is a temporary endocrine structure in mammals, involved in production of relatively high levels of progesterone and moderate levels of estradiol and inhibin A...

 after a Graafian follicle

Ovarian follicle

Ovarian follicles are the basic units of female reproductive biology, each of which is composed of roughly spherical aggregations of cells found in the ovary. They contain a single oocyte . These structures are periodically initiated to grow and develop, culminating in ovulation of usually a single...

 has expelled its secondary oocyte

Oocyte

An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...

 arrested in second meiosis

Meiosis

Meiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....

.

In microbiology

Microbiology

Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell , cell clusters or no cell at all . This includes eukaryotes, such as fungi and protists, and prokaryotes...

 and planktology

Planktology

Planktology is the study of plankton, various microorganisms that inhabit bodies of water. The field encompasses a variety of topics, including primary production, and energy flow. The carbon cycle is a recent area of interest....

 a theca is a subcellular structural component out of which the frustules

Frustule

A frustule is the hard and porous cell wall or external layer of diatoms. The frustule is composed almost purely of silica, made from silicic acid, and is coated with a layer of organic substance, which was referred to in the early literature on diatoms as pectin, a fiber most commonly found in...

 of diatoms

Diatom

Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...

 and dinoflagellates

Dinoflagellate

The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth...

are constructed.