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HEAD AND NECK - Editorial Comment

Editorial Comment (Editorial Overview Text Replicated on Overall Species page - Loxodonta africana - African Elephant

GENERAL HEAD STRUCTURE:
Adult:
Elephants have a huge head on a short neck. The ears of the African elephant are very large, fan-like and somewhat triangular in shape with a wide dorsal (top) edge but narrowing ventrally (towards the bottom). The elephant's trunk is derived from the upper lip and nose, extremely elongated and very muscular. On the tip of the trunk are located the nostrils, also both a dorsal and a ventral finger-like projection. It bears sensory hairs and is important in touch and olfaction. The trunk is extremely important for many of the elephant's daily activities. The mouth is relatively small. The elephant's skull is massive, containing many large sinuses which reduce its weight. The brain is situated ventrally towards the back of the skull.
Newborn: The newborn elephant has a relatively short trunk. The skull is much smaller, relative to the body, than in the adult, since the huge pneumatisation (expansion of air cavities) of the bones has not yet developed.

DENTITION:
Adult:
Elephants have the dental formula i 1/0, c 0/0, pm 3/3 m 3/3 (one upper incisor - the tusk, no canines, three premolars and three molars, i.e. six cheek teeth). The cheek teeth vary in size, with the first being smallest and the sixth being largest. each bears a number of ridges or laminae. The cheek teeth erupt from the caudal aspect of the jaw and progress forward, coming into wear sequentially, with one, or parts of two, molars in wear at any one time. The worn out tooth has its roots resorbed as it reaches the front of the mouth and the remains of the crown are spat out or swallowed. The movement of the teeth can be used for aging of elephants based on molar progression: which tooth is in wear and where it has reached in relation to a fixed landmark such as the foramen mentale in the mandible (jaw bone). The tusks are modified upper incisors. Initially they are capped with enamel but this is soon worn away. The main part of the tusk is composed of ivory, a form of dentine with a unique structure. The tusk grows throughout the elephant's life, from odontoblasts lining the sensitive pulp cavity, which contains blood vessels, nerves and connective tissue. Tusks of males grow more in both length and thickness than do those of females. Some individuals are born without tusks; this is probably genetic.
Newborn: At birth, the first and second molars are present in the jaw and these erupt soon after birth. The anterior end of the third molar erupts early also, so that for a time parts of three molars are in wear at the same time. Milk tusks or tushes, less than 5 cm long, cut the gum when the calf is about seven or eight months old; the permanent tusks appear at about 18 to 24 months.

EYES:
Adult:
The eyes, similar in size to those of humans, are anterolateral (half way between forward-facing and on the sides) on the head, half way between the trunk base and the ear orifice. They have a round pupil in a hazel or green iris. The eyelashes on the upper and lower lids are long. There is no functional lachrymal gland (tear gland) to produce tears nor any tear ducts to take fluid away from the eye. The eyes are moisturised from the secretions of the Harderian gland, which opens on the internal side of the third eyelid (nictitating membrane) and moisture either evaporates or drains down the side of the face.
Newborn:
Elephant calves are precocial, therefore the eyes are open and functional in the newborn calf.

(References are available in detailed literature reports below)

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General Head Structure

Adult SUMMARY: Elephants have a huge head on a short neck. The ears of the African elephant are very large, fan-like and somewhat triangular in shape with a wide dorsal (top) edge but narrowing ventrally (towards the bottom). The elephant's trunk is derived from the upper lip and nose, extremely elongated and very muscular. On the tip of the trunk are located the nostrils, also both a dorsal and a ventral finger-like projection. It bears sensory hairs and is important in touch and olfaction. The trunk is extremely important for many of the elephant's daily activities. The mouth is relatively small. The elephant's skull is massive, containing many large sinuses which reduce its weight. The brain is situated ventrally towards the back of the skull.

General:

  • The head is huge and the neck is short. (B147)

Ears:

  • The ears of African elephants are large and fan shaped; they may be 200 cm long from top to bottom. (B147)
  • The ears are large and fan-like with a lacy cartilage plate covered by the flattened pinna. There is a small slightly raised point corresponding the tragus. The ear is pear-shaped with the broad end upwards and the ear narrowing to a ventral point. There are stiff hairs around the ear orifice. (B453.1.w1)
  • Blood circulation in the periphery of the ears is relatively poor. (B10.49.w21)
  • There may be holes through the lower part of the earlobe of African elephants . (B147)
  • There is an intensive supply of blood vessels over the underside of the ears. (B147)
  • When it is hot, the veins stand out from the ear's medial surface. (B285.w3)
  • There are large subcutaneous blood vessels in a fan-like arrangement on the medial side of the ear. (B453.1.w1)
  • The blood vessels are contracted and not easy to find in cold external temperatures but during the heat of the day are distended, prominent and easily seen. (B453.1.w1)
  • The ears are large and triangular; the dorsal edge may be bent over medially, more so as the elephant gets older. In captive, but not in wild, elephants, the dorsal ear may turn over anteriorly instead. (B453.Intro.w13)
  • There are eight ear muscles, providing excellent range of movement and control of the ears. (B453.1.w1)
  • The ears are important in signaling and in temperature regulation. (B451.1.w1)
  • The ears measure about 183 cm by 114 cm. (B451.1.w1)
  • The ear flap is made up of a cartilaginous sheet covered with closely attached relatively thin skin. (B451.1.w1)
  • The top edge of the ear typically turns over backwards in mature African elephants. (B451.1.w1)
  • The ears are large and, when spread out to the sides, follow the line of the forehead, appearing to be a single mass. (B387.w4)
  • Along the upper edges of the ears is an overhanging flap, possibly providing a parasol effect. (B387.w4)
  • There is a rich network of blood vessels under the skin over the back of the ears. (B387.w4)

Trunk:

  • The trunk of elephants has developed from the upper lip and nose, becoming greatly elongated and muscularised. (B285.w3)
  • The trunk, an elongated nose, is very muscular and flexible; the nostrils are located at the tip, together with two fingerlike projections in African elephants, dorsal and ventral. (B147)
  • The trunk is slightly annulated; there is a dorsal and a ventral projection at the trunk tip. (B453.Intro.w13)
  • The heavily-muscled trunk has a good blood supply and a good supply of both sensory and motor nerves. (B10.49.w21)
  • The trunk contains six pairs of major muscles. The longitudinal muscles are mostly superficial; they are found in four segments: (B384.3.w3)
    • Dorsally are the levators, originating at the frontal bone; they extend the whole length of the trunk to the finger-like appendage on the trunk tip;
    • Ventrally are the depressors, which are used to curl the trunk up. These do not reach the extremity of the trunk. 
    • Laterally are the longitudinal bands, to bend the trunk from side to side.

    (B384.3.w3)

  • Transverse muscles, deep to the longitudinal muscles, are probably used for more complex movements. (B384.3.w3)
  • The trunk is derived from the upper lip and rhinarium and is innervated mainly by the infra-orbital branch of the second (maxillary) division of the fifth cranial nerve. (B453.1.w1)
  • The trunk is annulated and bears sensory hairs; it has both a dorsal and a ventral process at its tip. (B453.1.w1)
  • The trunk is very sensitive to both tactile and olfactory stimuli. (B453.1.w1)
  • The main trunk-raising muscle is the levator proboscidis, arising from the frontal bones and running longitudinally dorsally to terminate in the dorsal process of the trunk tip. (B453.1.w1)
  • The main trunk-lowering muscles are the depressores proboscidis, ventral muscles from the front of the premaxilla, with oblique fibres running longitudinally and laterally along the trunk in the outer laminae and in the reverse direction in the deeper laminae; these deeper fibres insert into a tendinous medial raphe. (B453.1.w1)
  • There are also muscles which act to dilate the nasal passages. From the ethmoid's lateral cartilage, muscle fans forward and laterally over the side of the skull, another portion with a similar origin fans posteriorly towards the summit of the skull, and a third portion originates in the septal cartilage. (B453.1.w1)
  • Radiating fibres arising from the walls of the nasal passages terminate on the skin. (B453.1.w1)
  • The trunk is, anatomically, the nose and upper lip. Paired nostrils run through the whole length. The skin covering the dorsal surface is annulated, with deep furrows, and is sparsely covered with sensory hairs. The trunk is completely muscular. (B451.1.w1)

Mouth:

  • The mouth, found below the trunk and with a thick, spout-like prehensile lower lip, is relatively small. (B453.1.w1)
  • Over the corners of the mouth, the trunk base is raised forming sulci (folds) over the tusk bases. (B453.1.w1)
  • Only slight lateral movements of the jaw are possible. (B453.1.w1)
  • A transverse line between the bases of the tusks marks the abrupt junction between the pigmented, cornified skin of the trunk and the smooth, unpigmented buccal skin. (B453.1.w1)
  • The tongue is relatively large and mobile, and takes up most of the space between the lower molars, but the free portion is short (about 7 cm / 2.33 inches in the adult) and the tongue cannot be protruded beyond the lower lip. (B453.2.w2)
  • Smooth mucous membrane lines the cheeks, gums and palate. (B453.2.w2)
  • The tongue bears many filiform papillae and fewer fungiform papillae. Posteriorly there are four to six circumvalate papillae arranged in a semicircle and on the tongue margins are found Mayer's foliate papillae, vertical laminae with intervening slits, about 30 in number. (B453.2.w2)
  • Just anterior to the epiglottis is the pharyngeal pouch, a diverticulum of the pharynx, bordered by the dorsal wall of the pharynx, the palate and the palatopharyngeal arch. (B453.2.w2)
  • There are three pairs of salivary glands (parotids, sub-maxillaries and sublinguals), also mucous glands, highly lobulated, found at the angle of the mandible. The ducts from the sub-mandibular glands open on either side of a filiform papilla on the frenulum. (B453.2.w2)

Skull:

  • The bones of the skull are greatly thickened. A system of air cells and cavities, interconnecting, reduces the total mass. (B147)
  • There are many air-filled sinus cavities in the huge skull. (B10.49.w21)
  • The cranium is domed. (B10.49.w21)
  • The premaxillary bones form the tusk sheaths. (B147)
  • A third of the length of the tusks is held within the alveolar processes of the skull; these grow as the tusks grow. (B10.49.w21)
  • The nasal bones are greatly shortened. (B147)
  • The skull makes up 12 - 25% of the elephant's body weight. (B285.w3)
  • The braincase is found behind the eyes and in line with the auditory canal. (B384.3.w3)
  • The main part of the skull is composed of sponge-like cancellous bone, with many thin-walled cavities between the two surfaces of each bone, which can be 30 cm apart, so that for their size the bones are relatively light. (B384.3.w3)
  • In elderly elephants, bone is absorbed wherever it is not require (wherever there is no stress on the bone). (B384.3.w3)
  • The skull of the female African elephant is relatively flattened in front with an angular point on the forehead; that of the bull is more rounded. (B384.3.w3)
  • The nasal turbinates are only rudimentary in elephants. (B384.3.w3)
  • The bones of the skull are greatly expanded by enlarged air spaces, lined by vascularised epithelium (mucous membrane) continuous with that lining the nasal cavities. The upward expansion of the roof of the skull provides a high origin point for the dorsal muscles of the neck, which then insert on the long neural spines of the cervical and thoracic vertebrae. (B453.1.w1)
  • The skull grows throughout the life of the elephant; its shape changes with age. (B453.1.w1)
  • The cranium is large and rounded. In the adult the cranium is much larger than the jaws and face. Bone thickness (frontal bone) may expand from 2.5 - 3.8 cm at term to 40 cm in a full-grown bull. (B453.1.w1)
  • The cow elephant has a distinct nuchal eminence whereas the nuchal crest of males forms a regular ridge across the top of the skull. The forehead of the cow then drops away to give a flat or slightly dished profile, in comparison to the slightly convex appearance of the bull. This can be used to determine sex in the field and in skulls. (B453.1.w1)
  • The mandibular condyles fit into the glenoid fossa allowing only a hinge action with very limited antero-posterior horizontal plane movements and extremely limited lateral movement of the mandible. (B453.1.w1)
  • The cerebral cavity is small relative to the cranium, situated posteriorly and ventrally. (B453.1.w1)
  • The maxillo-turbinates and naso-turbinates are absent, however ethmoturbinates are present, hanging down from the cribriform plate like book leaves. (B453.1.w1)
  • The mandible is massive. The mandibular rami join to form a distinct chin at the mandibular symphysis (only elephants and primates have a true chin). (B453.1.w1)
  • The bones of the skull are pneumatised. The face appears shorter and wider than that of the Asian elephant, and is longer from front to back. The jaw, triangular in profile, is longer than in the Asian elephant. The premaxilla is well developed, particularly in males, to hold the tusks. (B451.1.w1)
  • In female African elephants there is a ridge, the nuchal eminence, along the forehead, giving a "square" profile to the head which is distinguishable from that of the male, even in young animals. (B451.1.w1)
  • In the mature elephant the skull is greatly pneumatised. (B387.w4)
  • The bones of the roof and sidewalls of the braincase of the adult elephant are pneumatised, with extensive air cells, all interconnected and with perforations for blood vessels; dorsally, the total bone thickness including the air cells can reach 250 mm. (J397.70.w1)
Neonate / Young SUMMARY: The newborn elephant has a relatively short trunk. The skull is much smaller, relative to the body, than in the adult, since the huge pneumatisation (expansion of air cavities) of the bones has not yet developed.
  • Trunk:
    • The trunk is "diminutive" in young calves, not fully in proportion to the overall size of the calf. (B453.2.w2)
    • The trunk appears to be poorly controlled initially. (B384.5.w5)
  • Skull:
    • The air sinuses or cavities in the skull bones are much smaller in the young elephant than in the adult. (B212.w5)
    • The skull is relatively much smaller in the calf than in the adult, without the huge pneumatisation: e.g. the frontal bone may be only 2.5 - 3.8 cm thick, compared to 40 cm in an adult. (B453.1.w1)
    • The newborn elephant's skull is not pneumatised and the cranial bones are approximately 5-10 mm thick. (J397.70.w1)

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Dentition

Adult SUMMARY: Elephants have the dental formula i 1/0, c 0/0, pm 3/3 m 3/3 (one upper incisor - the tusk, no canines, three premolars and three molars, i.e. six cheek teeth). The cheek teeth vary in size, with the first being smallest and the sixth being largest. each bears a number of ridges or laminae. The cheek teeth erupt from the caudal aspect of the jaw and progress forward, coming into wear sequentially, with one, or parts of two, molars in wear at any one time. The worn out tooth has its roots resorbed as it reaches the front of the mouth and the remains of the crown are spat out or swallowed. The movement of the teeth can be used for aging of elephants based on molar progression: which tooth is in wear and where it has reached in relation to a fixed landmark such as the foramen mentale in the mandible (jaw bone). The tusks are modified upper incisors. Initially they are capped with enamel but this is soon worn away. The main part of the tusk is composed of ivory, a form of dentine with a unique structure. The tusk grows throughout the elephant's life, from odontoblasts lining the sensitive pulp cavity, which contains blood vessels, nerves and connective tissue. Tusks of males grow more in both length and thickness than do those of females. Some individuals are born without tusks; this is probably genetic.
  • Dental formula: i 1/0, c 0/0, pm 3/3, m 3/3, (B10.49.w, B147, B285.w3, B453.2.w2, B451.1.w1, W580.Sept2005.w1) giving a total of 26 teeth. (B147)
  • The tusks are the upper second incisors. (B384.3.w3)
  • There are no lower incisors, the upper first incisors and the canines are also absent. (B384.3.w3)
  • The jaws move backwards and forwards (with little sideways movement), so the teeth grate against one another like rasps. (B384.3.w3)
  • The jaws move up and down; they crush only those portions of food items which fall directly between the teeth. (B384.3.w3)

Cheek teeth:

  • It is most commonly accepted that the cheek teeth represent premolars II, III and IV and molars I, II and III; for many practical purposes they are simply referred to as molars I to VI. (B453.2.w2)
  • The cheek teeth are large and high crowned. Each tooth is made of transverse planes of dentine covered with enamel and filled with cement, which also covers the enamel ridges when the tooth is unworn. (B147)
    • Each tooth is made of complex ridges of dentine covered with enamel, with cement between the ridges. (B10.49.w21)
  • The first cheek tooth is smallest, with the fewest number of ridges; each succeeding molar is larger with more ridges. There are six sets of grinding teeth in total. (B147, B10.49.w21)
  • Usually only one set of cheek teeth is in wear at any one time. (B147)
  • Each molar, as it is worn away, is pushed forward and replaced by the next molar coming in obliquely from behind. The worn molar is usually pushed out in pieces. (B147)
    • The crown is worn and the blood supply is compromised by the succeeding tooth; the crown fractures transversely, the roots are resorbed and fractured sections of the old tooth crown are spat out or swallowed. (B10.49.w21)
  • The sixth cheek tooth is in wear for two fifths of the elephant's life. It is up to 21 cm long and more than 7cm wide, weighing nearly 4.0 kg. (B384.3.w3)
  • The six cheek teeth erupt in linear progression; each tooth appears caudally in the jaw and moves rostrally, becoming progressively worn down at the front and eventually dropping out. (B451.1.w1)
  • At any one time, one, or parts of two molars are in wear. In calves, parts of the first three cheek teeth may be in wear at the same time. (B451.1.w1)
  • Each molar has a series of laminae, ridges. When the tooth erupts the surface is rounded; the dentine of the ridges is covered with enamel. This wears down to leave exposed dentine with enamel surrounding, forming an efficient surface for rasping. (B451.1.w1)
  • Wear of the lower molars is faster and more regular than that of the upper molars. (B451.1.w1)
  • During chewing, the jaws move forwards and backward but there is little lateral movement. (B451.1.w1)
  • Molars have open roots filled with tooth pulp; the number of roots corresponds to the number of laminae. (B451.1.w1)
  • There is usually a gap between the roots of lamina 4 and lamina 5. (B451.1.w1)
  • Initially the roots are perpendicular to the tooth surface; later, as the tooth progresses forwards, the roots become inclined backwards. (B451.1.w1)
  • As the tooth moves forwards the anterior roots are resorbed, leaving an unsupported shelf of tooth, which is eroded from the front, breaks off and falls from the mouth or is swallowed. (B451.1.w1)
  • It is disputed whether the number of laminae per tooth is constant. (B451.1.w1)
    • Sikes claimed a set number of laminae per tooth in the African elephant, although with some laminae not always erupting through the gum. The set number is important for use of the progression of the teeth past the foramen mentale for age determination (see below: molar progression). (B451.1.w1)
    • Laws considered the number of laminae per tooth in the African elephant to be variable, including up to 14 in molar VI (compared with the 13 stated by Sikes). (B451.1.w1)
  • The length of time for which molar is in use varies: the first molar is shed after two years, while the sixth is in wear for 30 years. (B451.1.w1)
  • The molars have been said (by Laws) to be lost at two, six, 13-15, 28, 43 and about 65 years. (B451.1.w1)
  • Age at eruption is unclear. Molars I and II are present in the newborn and molar III by one year of age, with the first lamellae of molar IV being found by six years, of molar V at about 18 years, and of molar VI at about 30 years. (B451.1.w1)
  • Perhaps 10% of elderly elephants have a seventh molar; this is never as well developed as the other molars. (B451.1.w1)
  • The six molars move forward in linear progression from the proximal to the distal end of the jaw. (B453.2.w2)
  • Wear may vary between the left and right cheek teeth and between the upper and lower teeth. (B453.2.w2)
    • The right mandibular teeth may be used for the base-line description. (B453.2.w2)
  • Each cheek tooth is composed of dentine plates, bonded to the neighbouring plates by cementum, and covered with enamel. The plates become worn giving a rasp-like surface of lozenge-shaped ridges, as wide as 7.2 cm (2.5 in) in an old bull. (B453.2.w2)
  • The first three cheek teeth are much smaller than the later teeth, with thinner, "wavy" enamel and a more delicate general structure. The first tooth is very small (about twice the size of a human wisdom tooth) and is lost before the elephant is a year old; the second is in wear until the calf is four years old. (B462.3.w3)
  • Molar progression:
    • The first molar, with five laminae, is lost when the elephant is about two years old and the second, with seven laminae, at about four or five years. (B453.2.w2)
    • The third molar may form up to ten laminae although the tenth may not fully develop and even the ninth may become worn at the grinding surface of the tooth. Most of the laminae are in wear by four to five years. (B453.2.w2)
    • The fourth molar potentially has ten laminae but the first may only come into wear on the buccal side and the last may remain as a buttress below the tooth's grinding surface; it is usually fully in wear when the elephant reaches ten or eleven years of age. (B453.2.w2)
    • The fifth molar begins to move into wear when the elephant is about thirteen or fourteen and by about 23 to 25 years is probably fully in wear. There are twelve potential laminae; the first may only come into wear on the cheek side and the twelfth may be seen only as a small leaf on the face of the eleventh lamina; it does not usually come properly into wear. (B453.2.w2)
    • The sixth molar is the largest. It begins to come into wear when the elephant is about 28 to 30 years old. There are thirteen potential laminae although the last lamina may form a buttress against lamina 12, while the first lamina may only come into wear on the cheek side, forming a pillar. Anterior laminae may have been discarded by the time the posterior laminae come into wear. At its maximum, the tooth may give a 7.2 cm grinding width, 21 cm grinding length and may weigh 3.74 kg. (B453.2.w2)
    • When the last laminae of the sixth molar pass the foramen mentale it is no longer possible for the elephant to masticate food; this gives a practical limit for the elephant's life span. (B453.2.w2)

Tusks:

  • The tusk is the upper incisor, modified, which grows throughout the life of the elephant. Enamel is present only on the tip and is soon worn away. (B147)
  • The tusk, a modified incisor, is composed of dentine. Initially it is capped with enamel but this is soon worn away, leaving the dentine surrounding the pulp canal. (B10.49.w21)
  • The tusks of elephants are modified upper incisors. The ivory is made of a unique mixture of dentine and calcium salts, with a regular diamond pattern on cross section, which is not present in tusks of other mammals. (B285.w3)
  • Usually both males and females have tusks. (B10.49.w21)
  • Tusks of females usually weigh about seven kilograms and may weigh up to about 18 kg. The largest known tusk of a male was about 350 cm long and weighed about 107 kg. (B147)
  • The tusks grow continuously; in males both length and thickness increases throughout life while in females from about 15 years the diameter increases more slowly in relation to he length, producing more slender tusks, and only slow growth occur in animals more than 30 years old. (B147)
  • Tusks grow throughout the life of the elephant. (B462.3.w3)
  • In males, tusks are largest in mild individuals which avoid the fighting and tree ramming which may break the tusks. (B147)
  • The growth rate of tusks in elephants in Uganda is about 11 cm per year for a bull, 8.5 cm per year for a cow elephant. (B384.13.w13)
  • Theoretically, a bull could develop tusks 550 cm long and weighing 81 kg; due to breakage and general wear, 250 cm and 61 kg is the actual maximum reached. A cow could theoretically develop tusks 520 cm long and nearly 22 kg in length, but actually 155 cm and a little over 9 kg may be developed. (B384.13.w13)
  • The rate of weight increase of the tusks of bull elephants increases as the pulp cavity is filled. (B384.13.w13)
  • The centre of the tusk contains the tooth pulp: dentine-forming cells (odontoblastic cells) and connective tissue, well supplied with nerves. (B384.13.w13)
  • The pulp cavity is larger in bulls than in cows. In cows the pulp cavity increases in size until the cow is about 15 years old, then starts to fill in while in bulls it increases in size until the bull is at least 30 years old before starting to fill. (B384.13.w13)
  • The main part of the tusk is composed of dentine: a mineralised connective tissue with an organic matrix of the fibrous protein collagen and a mineral, inorganic component, dahllite, formed from calcium, phosphate and carbonate. Structurally, dentine is formed from microscopic dentinal tubules, radiating out from the pulp cavity; in elephant tusks these are arranged in a unique wavelike pattern. (B384.13.w13)
  • The dentine is surrounded by a layer of cementum, 3.0 - 5.0 mm thick near the gum region, which anchors the tusk in its socket. This is moderately calcified, softer than dentine and with a more bone-like structure. (B384.13.w13)
  • Initially there is a tip of enamel on the tusk, but this is only 0.75 mm thick and therefore, despite being very hard, is soon worn away. (B384.13.w13)
  • The roots of the tusks enlarge in length and diameter with age and penetrate between (and level with) the orbital fossa in older animals. (B453.1.w1)
  • The tusks may become stained reddish or black from tannins in tree bark. (B453.2.w2)
  • The adult tusk is constructed of dentine, initially with a cap of enamel, which is soon worn off. The base of the tusk, within the alveolus, is covered with cementum. Tusk dentine is continually deposited by odontoblasts over the conical surface of the tusk pulp and around its proximal rim. Skull growth occurs in proportion with tusk growth to accommodate most of the pulp-containing tusk within the maxillary and premaxillary bones. (B453.2.w2)
  • Elephants generally use one tusk more than the other; this tusk is often referred to as the servant, and generally grows thicker and denser, but is more blunted, than the other tusk. (B453.2.w2)
  • Accidental breakage of a tusk without exposure of the pulp causes only temporary discomfort. Breakage down to the pulp may result in abscessation. (B453.2.w2)
  • Elephant tusk dentine, ivory, has a unique pattern, developed from two systems of curving lines, both beginning at the centre of the tusk and curving smoothly to the periphery, one curving clockwise and the other anticlockwise, to produce diamond shaped areas on a transverse section, with smaller diamonds towards the centre and larger ones towards the periphery. (B453.2.w2)
  • Tusk shape varies and may show shared characteristics in a given elephant family. (B453.2.w2)
  • The tusks are upper incisors. (B451.1.w1)
  • Tusks grow throughout life, therefore older elephants bear larger, heavier tusks. (B451.1.w1)
  • There are genetic differences in tusk growth between elephants. (B451.1.w1)
  • The growth of tusks follows a sinusoidal curve. (B451.1.w1)
  • Tusks are made of dentine; initially there is an enamel cap, soon worn away. (B451.1.w1)
  • Approximately one quarter of the tusk is inside the tusk socket and is covered with cement. (B451.1.w1)
  • The tusk base is hollow. It contains the tusk pulp, consisting of blood vessels and nerves surrounded by mesenchymal connective tissue. (B451.1.w1)
  • Odontoblast cells deposit dentine over the surface of the pulp, so that the tusk grows from its base. (B451.1.w1)
  • In African elephants, both males and females generally have tusks. (B451.1.w1)
    • Males bear stouter, heavier tusks than do females. (B451.1.w1)
    • Some individuals are born tuskless. This is probably genetic: more than one tuskless individual will be found in a given family group. Lack of tusks affects appearance, with a sunken appearance to the upper lip where the tusks are normally found, and reduced growth of the posterior skull bones, where the neck muscles attach. (B451.1.w1)
  • One tusk is generally used more and becomes more worn. (B451.1.w1)
  • If the tusks cross over, the elephant has to move its trunk through the tusks to reach its mouth. (B451.1.w1)
  • Tusk growth in calves of about 4-5 years old increase in weight at about 2.0 g per day. (B451.7.w7)
  • There is genetic variation in exact tusk shape and in a group of elephants the tusks may show similar shapes. (B387.w4)
  • Tusks in the living animal are slightly flexible; long tusks may be seen to bend slightly when being used. (B387.w4)
  • Tusks grow at about 11 cm per year in males, 8.5 cm per year in females, but the ends get abraded and broken, reducing the length. (B387.w4)
Neonate / Young SUMMARY: At birth, the first and second molars are present in the jaw and these erupt soon after birth. The anterior end of the third molar erupts early also, so that for a time parts of three molars are in wear at the same time. Milk tusks or tushes, less than 5 cm long, cut the gum when the calf is about seven or eight months old; the permanent tusks appear at about 18 to 24 months.
  • Molars:
    • The first and second molars are present at birth. (B10.49.w21)
    • The first and second molars erupt soon after birth, at the same time as one another, and soon after this the anterior ends of the third molars erupt, so that the first two molars and part of the third molar are all in wear at the same time. (B453.2.w2)
    • As the molar progression starts ant the first molar reaches the foramen mentale, it appears that the anterior face of the crown and roots starts; a shelf of enamel and cementum projects anterior to the foramen mentale and parts are broken off. (B453.2.w2)
    • After the first two years of life, at any one time either one single molar or parts of two adjacent molars are in wear at any one time. (B453.2.w2)
  • Tusks:
    • Milk tusks are present before the permanent tusks. (B10.49.w21)
    • At birth, milk tusks are present; these fall out when the calf is about one year old, and are about 5 cm in length at this time. (B451.1.w1)
    • Deciduous tushes are present at birth and may reach 5 cm (2 inches) in length; at about one year these are replaced by the adult tusk. (B453.2.w2)
    • The milk tusks are less than 5 cm long, with a solid, tapering root and a small, enamel-tipped cap. They cut the gum when the calf is about five to seven months old. (B384.13.w13)
      • In the African elephant the milk tusks may be absorbed rather than being shed. (B384.13.w13)
    • The tusks appear when the calf is about 18 months to two years old; typically, they appear earlier in bull calves than in cow calves. (B384.13.w13)
    • By about two to three years of age the permanent tusks are visible. (B451.1.w1)

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Eyes

Adult SUMMARY: The eyes, similar in size to those of humans, are anterolateral (half way between forward-facing and on the sides) on the head, half way between the trunk base and the ear orifice. They have a round pupil in a hazel or green iris. The eyelashes on the upper and lower lids are long. There is no functional lachrymal gland (tear gland) to produce tears nor any tear ducts to take fluid away from the eye. The eyes are moisturised from the secretions of the Harderian gland, which opens on the internal side of the third eyelid (nictitating membrane) and moisture either evaporates or drains down the side of the face.
  • The eyes are positioned antero-laterally, midway between the external orifice of the ear and the base of the trunk. (B453.1.w1)
  • The eyeball is small for the size of the animal, being similar in size to that of humans. (B453.1.w1, B384.4.w4)
  • There are long eyelashes on the upper and lower eyelids. The eyelids are supported by cartilaginous tarsal plates. (B453.1.w1)
  • The iris is green or hazel. (B453.1.w1)
  • The pupil is round, the iris is usually hazel. (B384.4.w4)
  • The iris and pupil are round; the iris usually is hazel. (P80.1.w1)
  • The eyes have a paurangiotic retina; the retina appears pale with a few large blood vessels surrounding a pale optic disk. (B10.49.w21)
  • The nictitating membrane moves across the surface of the eye by means of a deep division of the orbicular muscle, unique to proboscians. (P80.1.w1)
  • There is no lachrymal apparatus. (B10.49.w21)
  • Moisture and lubrication for the eyes is supplied by the Harderian gland, on the internal surface of the nictitating membrane. (B10.49.w21)
  • The elephant has a nictitating membrane (third eyelid); a Harderian gland opens on the surface of the nictitating membrane. (B453.1.w1)
  • There is no functional lachrymal gland nor is there a functional lachrymal duct; tears (from the Harderian gland) evaporate or run down from the corner of the eye. (B453.1.w1)A Harderian gland opens onto the nictitating membrane; the lacrimal gland is vestigial and there is no lacrimal sac duct or pore. (P80.1.w1)
Neonate / Young SUMMARY: Elephant calves are precocial, therefore the eyes are open and functional in the newborn calf. 
  • Elephant calves are precocial, therefore the eyes are open and functional in the newborn calf. (B147)

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Authors & Referees

Authors Dr Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referees Susan K. Mikota DVM (V.w72)

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