Examples of follicle in the following topics:
-
- Follicle development signals the beginning of the menstrual cycle.
- At the start of the menstrual cycle, some 12-20 primary follicles begin to develop under the influence of elevated levels of follicle-stimulating hormone (FSH) to form secondary follicles.
- The primary follicles form from primordial follicles, which develop in the ovary as a fetus during conception and are arrested in the prophase state of the cellular cycle.
- The remaining follicle, called the dominant follicle, is responsible for producing large amounts of estrogen during the late follicular phase.
- This causes the secondary follicle to develop into a tertiary follicle, which then leaves the ovary 24–36 hours later.
-
- During the follicular phase, follicle-stimulating hormone (FSH) is secreted by the anterior pituitary gland.
- The rise in FSH levels recruits five to seven tertiary-stage ovarian follicles (also known as Graafian or antral follicles) for entry into the menstrual cycle.
- These follicles compete with each other for dominance.
- This slowdown in LH and FSH production leads to the atresia (death) of most of the recruited follicles, though the dominant follicle continues to mature.
- This in turn causes increased levels of FSH, leading to recruitment of follicles for the next cycle.
-
- The rise in FSH recruits tertiary-stage ovarian follicles (antral follicles) for entry into the menstrual cycle.
- Follicle-stimulating hormone induces the proliferation of granulosa cells in the developing follicles and the expression of luteinizing hormone (LH) receptors on these cells.
- Many endocrinologists believe that the estrogen secretion of the dominant follicle lowers the levels of LH and FSH, leading to the atresia (death) of most of the other recruited follicles.
- The ovum then leaves the follicle through the formed stigma.
- Increased levels of FSH start recruiting follicles for the next cycle.
-
- Acne, clinically known as acne vulgaris, is a common human skin disease affecting skin with the densest population of sebaceous follicles such as the face, upper parts of the chest, and back .
- Acne develops as a result of blockages in hair follicles.
- Bacteria becomes trapped in these clogged follicles, producing pus and inflammation as the immune system attempts to destroy the bacteria.
- The sebaceous gland produces oily secretions that can block the follicle, resulting in a pimple.
-
- The root is part of the
hair enclosed by the hair follicle, which is itself a tube-like involution of
the skin.
- In the deepest portion of
the each hair follicle lies the hair bulb.
- Attached to a hair follicle is a bundle of
muscle fibers.
-
- If the pituitary gland is removed, spermatogenesis can still be initiated by follicle-stimulating hormone (FSH) and testosterone.
- Follicle-stimulating hormone (FSH) is released by the anterior pituitary gland.
- Follicle-stimulating hormone stimulates both the production of androgen-binding protein by Sertoli cells and the formation of the blood-testis barrier.
-
- Male baldness is the result of genetic sensitivity of hair follicles to dihydrotestosterone that causes hair follicles to atrophy.
- Male pattern baldness is caused by a genetic sensitivity of hair follicles to dihydrotestosterone (DHT).
- In genetically-prone scalps, i.e. those experiencing male or female pattern baldness, DHT initiates a process of follicular miniaturization in which the hair follicle begins to deteriorate.
- In time, hair becomes thinner and its overall volume is reduced, resembling fragile vellus hair or "peach fuzz" until, finally, the follicle falls dormant and ceases producing hair completely.
- Recent research suggests that elevated levels of the enzyme prostaglandin D2 synthase and its product prostaglandin D2 (PGD2) in hair follicles contribute to androgenetic alopecia.
-
- Chemotherapy causes hair loss by killing cells that divide rapidly, one of the main properties of most cancer cells and hair follicles.
- Chemotherapy also harms cells that divide rapidly under normal circumstances, such as cells in the bone marrow, mouth, nail beds, and hair follicles.
-
- Sebaceous glands can usually be found in hair-covered areas where they are connected to hair follicles to deposit sebum on the hairs, and bring it to the skin surface along the hair shaft.
- The structure consisting of hair, hair follicle, and sebaceous gland is also known as pilosebaceous unit.
-
- The
developing egg cell (or oocyte) grows within the environment provided by ovarian
follicles.
- Follicles are composed of different types and number of cells
according to their maturation stage, which can be determined by their size.
- When oocyte maturation is completed, a luteinizing hormone (LH) surge secreted by the pituitary
gland stimulates follicle rupture and oocyte release.
- The follicle remains functional and transforms into a corpus
luteum, which secretes progesterone to prepare the uterus for possible embryo implantation.