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The human earlobe (''lobulus auriculae''), the lower portion of the
outer ear The outer ear, external ear, or auris externa is the external part of the ear, which consists of the auricle (also pinna) and the ear canal. It gathers sound energy and focuses it on the eardrum (tympanic membrane). Structure Auricle The ...
, is composed of tough
areolar Loose connective tissue, sometimes called areolar tissue, is a cellular connective tissue with thin and relatively sparse collagen fibers. Its ground substance occupies more volume than the fibers do. It has a viscous to gel-like consistenc ...
and
adipose Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular ...
connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...
s, lacking the firmness and elasticity of the rest of the auricle (the external structure of the ear). In some cases the lower lobe is connected to the side of the face. Since the earlobe does not contain
cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...
it has a large
blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...
supply and may help to warm the ears and maintain balance. However, earlobes are not generally considered to have any major biological function. The earlobe contains many
nerve ending A free nerve ending (FNE) or bare nerve ending, is an unspecialized, afferent nerve fiber sending its signal to a sensory neuron. ''Afferent'' in this case means bringing information from the body's periphery toward the brain. They function as cu ...
s, and for some people is an
erogenous zone An erogenous zone (from Greek , ''érōs'' "love"; and English ''-genous'' "producing", from Greek , ''-genḗs'' "born") is an area of the human body that has heightened sensitivity, the stimulation of which may generate a sexual response, su ...
. The zoologist
Desmond Morris Desmond John Morris FLS ''hon. caus.'' (born 24 January 1928) is an English zoologist, ethologist and surrealist painter, as well as a popular author in human sociobiology. He is known for his 1967 book ''The Naked Ape'', and for his televisi ...
in his book ''
The Naked Ape ''The Naked Ape: A Zoologist's Study of the Human Animal'' is a 1967 book by English zoologist and ethologist Desmond Morris that looks at humans as a species and compares them to other animals. '' The Human Zoo'', a follow-up book by Morris th ...
'' (1967) conjectured that the lobes developed as an additional erogenous zone to facilitate the extended sexuality necessary in the evolution of human monogamous pair bonding.


Organogenesis

The earlobe, as a body part built of
epithelium Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...
and
connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...
, might appear to be derived from
dermatome Dermatome may refer to: * Dermatome (anatomy), an area of skin that is supplied by a single pair of dorsal roots * Dermatome (embryology), the portion of the embryonic paraxial mesoderm, the somite, which gives rise to dermis * Dermatome (instrument ...
. But this is not the case, as in the surrounding tissue there are no
somite The somites (outdated term: primitive segments) are a set of bilaterally paired blocks of paraxial mesoderm that form in the embryonic stage of somitogenesis, along the head-to-tail axis in segmented animals. In vertebrates, somites subdivide in ...
s and thus no dermatome. In this area, the
dermis The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided i ...
is derived from cells of mesenchymal cells: the mesenchyme is derived from the
sclerotome The somites (outdated term: primitive segments) are a set of bilaterally paired blocks of paraxial mesoderm that form in the embryonic stage of somitogenesis, along the head-to-tail axis in segmented animals. In vertebrates, somites subdivide in ...
and splanchnopleura located in the nearby regions of the
torso The torso or trunk is an anatomical term for the central part, or the core, of the body of many animals (including humans), from which the head, neck, limbs, tail and other appendages extend. The tetrapod torso — including that of a human ...
. The earlobe as a body part arises and develops in the vicinity of auricular follicle, as a result of cascade induction: # The first-level inductor is the central segment of Archenteron's roof, which induces the production of the
Medulla oblongata The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involun ...
(part of the
Hindbrain The hindbrain or rhombencephalon or lower brain is a developmental categorization of portions of the central nervous system in vertebrates. It includes the medulla, pons, and cerebellum. Together they support vital bodily processes. Metencephalo ...
). # The second-level inductor is the
Medulla oblongata The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involun ...
, which induces the production of a pair of auricular follicles derived from the
mesoderm The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical E ...
. # The third-level inductor is the auricular follicle, which induces the production of the
auditory bulla The tympanic part of the temporal bone is a curved plate of bone lying below the squamous part of the temporal bone, in front of the mastoid process, and surrounding the external part of the ear canal. It originates as a separate bone (tympanic ...
.


Genetics

Earlobes average about 2 centimeters long, and elongate slightly with age. Although the "free" vs. "attached" appearance of earlobes is often presented as an example of a simple "one gene – two alleles" Mendelian trait in humans, earlobes do not all fall neatly into either category; there is a continuous range from one extreme to the other, suggesting the influence of several genes.Mader S. S. (2000): Human Biology. McGraw–Hill, New York, .


Clinical issues

Earlobes are normally smooth, but occasionally exhibit creases. Creased earlobes are sometimes associated with genetic disorders in children, including Beckwith-Wiedemann syndrome. In some early studies, earlobe creases were thought to be associated with an increased risk of
heart attack A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may tr ...
and
coronary heart disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves the reduction of blood flow to the heart muscle due to build-up of atherosclerotic pla ...
. But more recent studies have concluded that, since earlobes become more creased with age, and older people are more likely to have heart disease than younger people, age rather than intrinsic factors may account for the findings linking heart attack to earlobe creases. The earlobe crease is also called
Frank's Sign Frank's sign is a diagonal crease in the ear lobe extending from the tragus across the lobule to the rear edge of the auricle. The sign is named after Sanders T. Frank. It has been hypothesised that Frank's sign is indicative of cardiovascul ...
.


Society and culture


Earlobe piercing and stretching

Piercing the earlobes is a commonplace activity in many cultures in many historical eras; no other location on the body is as commonly pierced. Consequently, injury to the earlobe due to the weight of heavy earrings is also common. Some cultures practice
earlobe stretching Stretching, in the context of body piercing, is the deliberate expansion of a healed piercing for the purpose of wearing certain types of jewelry. Ear piercings are the most commonly stretched piercings, with nasal septum piercings, tongue piercin ...
for decorative effects, using piercing ornaments to stretch and enlarge the earlobes to accommodate plugs.


Negative effects of wearing earrings

Some research has found that the most frequent complications connected with wearing earrings are: *
inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...
, *
keloid Keloid, also known as keloid disorder and keloidal scar, is the formation of a type of scar which, depending on its maturity, is composed mainly of either type III (early) or type I (late) collagen. It is a result of an overgrowth of granulation t ...
s, * loss of tissue by tearing, and * mechanical division of earlobes. A noticeable relationship has been found by Polish scientists between the piercing of young girls' earlobes and their subsequently developing allergic skin reactions.Harmful earrings (pl. Szkodliwe kolczyki)
Fizjointormator. Retrieved 2015-04-01

Tvn24 Retrieved 2015-04-01
In the view of Professor Ewa Czarnobilska, the manager of the research team, the primary reason for the allergies connected to earrings is the presence of
nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
, which is a common component of the alloys used in jewelry production and leaches from the earrings. The symptom seen is generally
eczema Dermatitis is inflammation of the Human skin, skin, typically characterized by itchiness, erythema, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become lichenification, thick ...
, and is often misdiagnosed as a
food allergy A food allergy is an abnormal immune response to food. The symptoms of the allergic reaction may range from mild to severe. They may include itchiness, swelling of the tongue, vomiting, diarrhea, hives, trouble breathing, or low blood pressure ...
, for instance to milk. The specific mechanism in allergies caused by earrings is the contact of nickel ions with the
lymphatic system The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system, and complementary to the circulatory system. It consists of a large network of lymphatic vessels, lymph nodes, lymphatic or lymphoid o ...
. The study noted that children who stopped wearing earrings did not see the disappearance of the allergic symptoms. The
immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...
remembers the presence of the nickel ions in the person's
blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...
and
lymph Lymph (from Latin, , meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues to ...
, so the child can still react to: * metal parts of wardrobe, *
dental braces Dental braces (also known as braces, orthodontic cases, or cases) are devices used in orthodontics that align and straighten teeth and help position them with regard to a person's bite, while also aiming to improve dental health. They are often ...
, *
dental prosthesis A dental prosthesis is an intraoral (inside the mouth) prosthesis used to restore (reconstruct) intraoral defects such as missing teeth, missing parts of teeth, and missing soft or hard structures of the jaw and palate. Prosthodontics is the den ...
, *
orthotics Orthotics ( el, Ορθός, translit=ortho, lit=to straighten, to align) is a medical specialty that focuses on the design and application of orthoses, or braces. An is "an externally applied device used to influence the structural and functio ...
, * meals cooked in pots with addition of nickel, * margarine (nickel is a catalyst in hydrogenation of unsaturated fats), * coins, * chocolate, * nuts, * leguminous vegetables, * wine, and * beer. Research by allergists has found that in a sample of 428 pupils of ages 7–8 and 16–17 years old: * 30% of the research population showed an allergy to nickel, and * the allergy occurred in girls who had started wearing earrings in early childhood.


References


Further reading

* {{Authority control Ear de:Ohrmuschel#Ohrläppchen