Human Development and Its Theories
Mohamed Ahmed Abd El-Hay in Understanding Psychology for Medicine and Nursing, 2019
At 16 weeks, teeth buds have formed and fingernails are forming. By 18–20 weeks, an ultrasound scan should be able to identify the sex if the baby is in a position that allows the genitals to be seen. At 20 weeks, bone is forming from cartilage. Hair and eyelashes are also present. The mother can feel the baby moving. At six months, the fetus’s brain activity becomes similar to that of a newborn baby, and the baby’s skin is covered by a protective paste called vernix. In the eighth and ninth months, the baby stores fat and approximately doubles in weight. This additional body fat will help the newborn adjust to changing temperatures outside the womb. It also contributes to the newborn’s chubby appearance. As birth approaches, growth slows and the fetus’s body systems become more active.
Hair Morphology, Biogenesis, Heterogeneity, Pathophysiology and Hair Follicle Penetration
Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters in Cosmetic Formulation, 2019
Although not visible at first sight, the hair and the hair follicle provide multiple functions in humans. First, the hair is a sensory organ. The autonomous nervous system can induce the erection of the hair, which is controlled by the arrector pili muscle leading to so-called goosebumps which are mainly triggered by coldness, anxiety or emotions (Benedek and Kaernbach, 2011). Animals use this effect to appear larger and more threatening to their enemies; for men, this function seems to play a subordinate and sometimes even annoying role (Benedek and Kaernbach, 2011). Moreover, hairs provide several protective functions. Eyelashes and eyebrows, for example, can prevent sweat and foreign particles from reaching the eyes. Scalp hair offers efficient sun protection (Parisi et al., 2009) as can be seen in the high incidence of skin cancer on the scalp of bald men. Nowadays, scalp hair is a very important instrument of psychosocial communication. A loss of scalp hair frequently induces severe psychological strain (Katoulis et al., 2015).
Musculoskeletal disorders and connective tissue disorders
Steve Hannigan in Inherited Metabolic Diseases: A Guide to 100 Conditions, 2018
This disorder usually presents between 9 and 24 months of age. Symptoms that may be apparent at birth (congenital symptoms) include dry shiny hard skin over the lower half of the body, and certain characteristic facial features, including bluish discoloration and nose abnormalities. Symptoms that appear later include severe growth delay and low weight for the height of the individual, underdevelopment of the facial bones (causing a small jaw, a small face and prominent forehead), prominent eyes, thin lips and prominent ears with missing ear lobes. Hair loss may be apparent, and eyebrows and eyelashes may disappear with age. Dental abnormalities may also be present. Individuals with this disorder lose the layer of fat beneath the skin, and may have skeletal abnormalities that include loss of bone density (osteoporosis), degenerative changes that afect many bones in the body, hip deformities, and abnormal tissue forming around some joints, causing joint stifness and mobility problems. Afected individuals may have an awkward stance and a characteristic walk.
The role of lid margin structures in the meibomian gland function and ocular surface health
Published in Expert Review of Ophthalmology, 2021
Sezen Karakus, Xi Dai, Xi Zhu, John D Gottsch
The eyelashes are nearly always curved in individuals [18]. A downward vertical malposition of the eyelashes is called lash ptosis and may be an indicator of structural abnormalities [22]. (Figure 3) Excess skin or fatty tissue, such as in dermatochalasis, is the most common reason for lash ptosis [22]. Floppy eyelid syndrome is another condition that is associated with lash ptosis. In fact, lash ptosis and the loss of eyelashes are characteristics of the syndrome. Eyelid laxity in floppy eyelid syndrome due to elastin deficiency in the tarsal plate is responsible for the altered direction of the eyelashes [23–25]. Lash ptosis may be an indicator of reduced tension of orbicularis oculi and Riolan’s muscle, which can explain meibomian gland dysfunction even if the orifices are not obstructed.
Eye Make-up Products and Dry Eye Disease: A Mini Review
Published in Current Eye Research, 2022
Mazyar Yazdani, Katja Benedikte Prestø Elgstøen, Tor Paaske Utheim
Eyelashes (cilia) protect the eye from potential incoming danger through the reflective response, defend the eye against particles using its curved shape, help to keep the moisture of the eye by minimizing airflow, filter out sunlight, and provide natural beauty. There are typically 2–3 rows of lashes on each lid rim. The upper eyelashes differ in number (100–150), length (8–12 mm), and shape (curved upward) compared to the lower ones (50–75 and 6–8 mm, respectively). With a normal lifetime of 5–12 months, the eyelashes grow ~0.15 mm per day, depending on age and the physical health of individuals. The eyelashes are housed in the muscular layer and are typically concomitant with two glands of Zeis (modified sebaceous gland) and often the apocrine gland of Moll (a modified sweat gland).24
Oral isotretinoin combined with topical clobetasol 0.05% and tacrolimus 0.1% for the treatment of frontal fibrosing alopecia: a randomized controlled trial
Published in Journal of Dermatological Treatment, 2022
Hamidreza Mahmoudi, Anahita Rostami, Soheil Tavakolpour, Ali Nili, Amir Teimourpour, Ali Salehi Farid, Robabeh Abedini, Mohammad Amini, Maryam Daneshpazhooh
Frontal fibrosing alopecia (FFA) is a primary cicatricial alopecia, initially described by Kossard in 1994 (1). It is characterized by progressive frontotemporal and eyebrows’ hair loss, perifollicular erythema, and hyperkeratosis; however, it can affect the entire margin of the scalp. Loss of body hair and eyelashes may also occur (2). Although FFA is more frequent among postmenopausal women, premenopausal women and rarely men may also be affected. The exact pathogenesis of FFA has not been understood so far; inflammatory cells infiltration within the hair follicle bulge – where the stem cells are located – may lead to permanent hair loss. Defective lipid metabolism, deficiency in peroxisome proliferator-activated receptor (PPAR)-c-mediated signaling, and proinflammatory cytokines such as interferons have been proposed to contribute to FFA pathogenesis (3).
Related Knowledge Centers
- Cornea
- Corneal Reflex
- Ectoderm
- Eye
- Eyelid
- Hair Follicle
- Sex
- Nerve
- Hair
- Arrector Pili Muscle