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The tongue (lingu, glossa)
Is muscular membrane filing the mouth cavity, between body of mandible, it fills the oral
cavity proper, the shape of it different according to the species of animal, it consist of:
1-the root (radix lingua): is the caudal part of tongue which attached to the hyoid bone , soft
palate and pharynx , only the dorsal part of it is free.
2-the body: Is the middle part of tongue attached to the mandible , and has three surfaces, except
in dog have two surfaces:
A-dorsal surface (dorsum).
B-lateral surface: it is flat, become round
and narrow cranially.
C-ventral surface: is attached with
geniohyoideus and mylohyoideus muscle.
3-the apex (toe): Is the free part which is
spatula shape and have upper and lower
surface and two borders(rounded), from
the lower surface of apex, there is a fold of
mucous membrane fold bases to the floor
of oral cavity, form the frenulum linga.
Function of lingua:
1-main fold for the intake solid and liquid.
2-it is important tactile organ taste of food.
3 it is important in the mastication of food
swallowing.
4-can is use for cleaning the skin and hair.
Structure of tongue
1-Intrinsic muscle: they are form the
substance of tongue and they are run
longitudinally, vertical and transverse direction.
2-Lingual glands: found between the intrinsic muscles .
3-Mucous membranous: it covers the intrinsic muscles, the mucous membrane of dorsal
surface have two types of papillae according to the function:
A-Mechanical papillae:
1-Conical papillae in shape located on the caudal third of the tongue dorsum .
2-Lenticular papillae in shape: large and
wide papillae.
3-Filliform papillae are soft or smooth
horny threats.
B-Gustatory papillae:
1-Fungiform: they are large and easy in seen, rounded at the free end, they are found in the lateral
part of the tongue and dorsal surface.
2-Vallate papillae: are found on the caudal part of dorsum rostral to the root of the tongue. They
are circled by a cleft filled with taste buds.
3-The foliate papillae : are situated just rostral to the palatoglossal arches of he soft palate , where
they form round eminence.
Species differences :
1- torus linguae : around swelling of the caudodorsal surface of the ox tongue.
2- Lingual fossa : depression in front of the ox torus linguae. This is a site of penetration of the
foreign objects .
3- Tongue cartilage : the dog has a bar of cartilage(lyssa = cylindrical fibrous tissue enveloping
fat & muscle (located ventrally at apex in carnivores). The horse has a similar structure
embedded in the median plane of the dorsal surface.
4- In horse the conical papillae and lenticular papillae absent , and the vallate papillae are usually
two or three in number.
5- The tunica mucosa of the tongue of ox is often pigmented and may be spotted.
6- In ox the apical half of the dorsum , rostral to the torus , is covered by filiform papillae directed
caudally , these are cornified and sharp , especially on the apex, and impart the roughness
which makes the bovine tongue an efficient organ of prehension in grazing. In the sheep and
goat the papillae are soft and the tongue is smooth ; it dose not act as a prehensile organ.
7- Lenticular papillae and conical papillae are found in the ruminant and the vallate papillae in ox
and goat 8-17 in number form an irregular double row on each side of the caudal part of the
dorsum, in sheep they number 18-24 on each side . foliate papillae absent in ruminant
Innervation of the tongue :
1-taste (special sense): the sense of the rostral two third of the tongue is carried over the chorda
tympani nerve, a branch of facial nerve .
2-taste from the caudal third of the tongue passes by the glossapharyngeal and vagus nerves.
3-sensation (pain , temperature and tactile) : carried over the lingual branch of the mandibular
nerve.
4-motor innervation : by the hypoglossal nerve.
Vessels : the arteries of the tongue are the lingual and sublingual branches of the linguofacial
trunk .
The veins go to the linguofacial and maxillary veins.
The lymph vessels : go chiefly to the retropharyngeal lymph nodes
Teeth : or dentes : These tissues vary somewhat in their arrangement in the two main
types of tooth. (Note: not all teeth can be classified into these types).
1-low-crowned or brachydont teeth (brachys =short +odous=tooth), which have deep
roots in relation to the crown; the crown is covered in enamel, and in general the teeth stop
growing once they have reached adult size. This is the kind of tooth found in man, dogs ,
pig and ruminants .
2-high-crowned or hypsodont teeth(hipsos=height,+odous=tooth)(overgrowing) ,the
teeth having no distinct neck, which have high crowns in relation to the roots; the crown is
covered in cement as well as enamel, and enamel also extends into the root. The teeth may
retain the potential for growth throughout life .As the surface wears down (by about 2-3mm
per year), the pulp cavity may become exposed, but this is sealed off by secondary dentine
formed as result of odontoblast activity. This is the kind of tooth found in herbivores,
including the horse.
*Each tooth is suspended in its bony socket, the alveolus, by a dense, irregular collagenous
connective tissue, the periodontal ligament. The gingival also supports the tooth, and its
epithelium seals the oral cavity from the subepithelial connective tissue spaces. The portion
of the tooth that is visible in the oral cavity is called the crown, whereas the region housed
within the alveolus is known as the root. The portion between the crown and the root is the
cervix(neck).
The entire tooth is composed of three calcified substances, which enclose a soft, gelatinous
connective tissue, including sensory nerves , arteries , veins , lymphatic and primitive
connective tissue called the pulp , located in a continuous space subdivided into the pulp
chamber and root canal. The root canal communicates with the periodontal ligament space
via a small opening, the apical foramen, at the tip of each root. It is through this opening
that blood and lymph vessels as well as
nerves enter and leave the pulp.
The mineralized structures of the
tooth are enamel, dentin, and
cementum.
Surface of teeth – Dentine: similar to
bone, is formed by odontoblasts at base
of dentine layer forming the bulk of the
tooth; these remain alive for life of tooth.
Dentin surrounds the pulp chamber and
root canal and is covered on the crown
by enamel and on the root by cementum
– Enamel: the hardest substance in the
body, is formed of hexagonal prisms of
hydroxyapatite. Formed by ameloblasts, which disintegrate after enamel is formed; thus it
cannot undergo repair. It covers only the crown in low-crowned teeth and covers the crown
and body in high-crowned teeth.
– Cementum : similar to thin bone, contains collagen fibers “which extend into bony
socket (alveolus); they form periodontal membrane which holds tooth in place . the
cementum covers the root only in low-crowned teeth and covers the entire tooth in highcrowned teeth.
Thus, the bulk of the hard substance of the tooth is composed of dentin, Enamel and
cementum meet each other at the cervix of the tooth.
The morphology of teeth:
1-free surface (tabil surface): is the cutting surface of incisors or canines.
2-vestibular surface: are the sides next to the vestibule, the vestibular surface of incisors and
canines called labial surface and the vestibular surface of premolar molar called buccal surface or
cheeks surface
3-inner surface (lingual surface) is contact with tongue.
4-side surface (contact): that surface which is contact
with the adjacent teeth in the same jaw.
The teeth in mammals have different functions in
different parts of the oral cavity:
1-Incisors: are most cranial in position , which are
brachydont in dogs, but hypsodont in horses, are used
for cutting off pieces of food (mainly in herbivores).
Normally three on each side, upper and lower.
3-Canines: are following the incisors, and used for
grasping food (carnivores) and for offence. Are absent in ruminants, and most mares. An
interdentally space separates canines from cheek teeth. C (Canine) = 1 pairs
3-Cheek teeth: (premolars, molars) which are more complex, may be brachydont (dog,)
or hypsodont (horse), they are located on the side of jaw, therefore called also cheek teeth or
buccal teeth. P (premolar) = 4 pairs. M (molar) =3 pairs.
Deciduous dentition : the baby teeth (milk teeth) developing early in life, giving the young
animal a functional set of teeth. They smaller and fewer in number than the permanent
dentition.
Permanent dentition: the second set of teeth replacing the deciduous dentition as the jaw
lengthens. They must last the life of animal.
Dental formula: a shorthand represented indicating the number of teeth of an animal. Duee
to bilateral symmetry .
Comparative:
Ruminants such as cattle, sheep and goats are herbivores with a
unique digestive anatomy. A prominent feature of ruminant dental
anatomy is that they lack upper incisors, having instead a "dental
pad
Dental Formulae
Deciduous
003
= 10 Permanent
313
0033
= 16
3133
Tooth Eruption
Deciduous
Permanent
Incisors
Birth - 2 weeks
18 - 48 months
Premolars
Birth - 1 weeks
24 - 36 months
6 - 30 months
Molars
In horse : The molars and premolars of the horse are known as cheek teeth. The cheek teeth
slowly erupt to compensate for the constant grinding which wears away 2-3mm per year.
For this reason, horses have very long teeth that are referred to as hypsodont which means
"high tooth."
Dental Formulae
Deciduous
303
3 1 3(4) 3
= 12 Permanent
= 20(21)
303
3133
This skull is from a young horse shown by the long cheek teeth. In the maxillary arcade the
cheek teeth extend into the
maxillary sinus. The cheek
teeth do not always wear away
evenly
resulting
in
the
formation of hooks and points.
These hooks and points can cut
into the tongue and buccal
mucosa
causing
great
discomfort to the animal. To
avoid this, horses need to
have their teeth ground down
with a rasp periodically - a
procedure called "floating.
The upper first premolars of
horses are known as "wolf teeth".
In dog : dental formula are :
Perminant:2(I3/3 C 1(O)/1(0) P3(4)/3 M3/3)=36-42
3/3)=28
In cat : dental formula are :
Perminant:2(I3/3
C
1/1
P3/2
M1/1)=30
Deciduous : 2(I 3/3 C1/1 P 3/2)=22
In pig :
Swine are omnivores and there is probably no other animal
that is quite as focused on food. Give a pig a treat (like the
animal cracker in the mouth of the little pig to the right) and
they'll do almost anything. Piglets are born with "needle teeth"
which are the deciduous third incisors and the
Mandibular
Arcade Lateral View
canines.They project laterally from the gums and can injure the
sow or other piglets so are often clipped off within hours of
birth.
In boars, the canine teeth, or tusks, grow
: throughout the animal's life. The lower tusks are kept sharp by
friction against the upper ones making them formidable
weapons. Numerous tubercles make the occlusal surface of the
molars irregular, ideal for crushing food.
Maxillary Arcade Lateral View
Deciduous : 2(I 3/3 C1/1 P
Dental Formulae
Deciduous
3 1 3
= 14 Permanent
313
3 1 4 3
= 22
3143
Tooth Eruption
Deciduous
Permanent
Incisors
Birth - 2 weeks
8 - 18 months
Canines
Birth
8 - 12 months
Premolars
2 weeks - 8 month
12 - 16 months
Molars
Hyoid bone
Hyoid bone is situated chiefly between the rami
of the mandible, built dorsal part extend some
4 - 22 months
what further caudal, it is attached to the styloid process of the petrous part of the temporal bone by
the rods of cartilage, the tympanohyoid and supports the root of the tongue, the pharynx and the
larynx ,it consist of many parts:
1-the basihyoid (body): is short transverse bar, compressed dorsoventrally. They basihyoid,
lingual process and thyrohyoid are fused to spur or a fork with very a short handle.
2-lingual process: a project rostral medially from the basihyoid and it is embedded in the root of
the tongue during life. it is compressed laterally and has a blunt pointed free end.
3-The thyrohyoid: these correspond to the great cornea of extend caudally and dorsally from the
lateral
parts of the basihyoid. They are compressed laterally and the caudal end has a short cartilaginous
prolongation which is connected with the rostral cornu of the thyroid cartilage of the larynx.
4-The ceratohyoids (small cornu): are short rods which are directed dorsally and rostrally from
either end of the body, the ventral end has a small concave facet which articulate with the
basihyoid, the dorsal end articulate with stylohyoid or with epihyoid when present.
5-The stylohyoid: are much the largest parts of the bone .they are directed dorsally and caudally
are connected dorsally with the base of the petrous part of the temporal bones:
A-the dorsal extremity: is large and forms two angles:
1-the articulate angle is connected by a rod of cartilage (the tympanohyoid), with the styloid
process of the petrous part of the temporal bone.
2-the muscular angle is thickened and rough for muscular attachment.
B-the ventral extremity is small and articulate with ceratohyoid or epihyoid.
6-The epihyoid: are small, wedge shaped pieces or nodules interposed between the ceratohyoids
and stylohyoids. They are usually transitory and unite with the styloids in the adult.
Hyoid muscles:
This is group consisting of eight muscles, one of which, the hyoideus transversus is un paired:
1-The mylohyoideus muscle: together with its fellow from a sort of sling between the molar parts
of the mandible, in which the tongue is supported.
Origin: the medial surface of the alveolar border of the mandible.
Insertion: the lingual process, basihyoid bone and thyrohyoid bone.
Action: it raises the floor of the mouth, the tongue and the hyoid bone.
2-Stylohyoideus muscle: is a slender and fusiform muscle having direction nearly parallel to that
of the thyroid bone.
Origin: the muscular angle of the dorsal extremity of the thyrohyoid bone.
Insertion: the rostral part of thyrohyoid bone.
Action: it draws the base of the tongue and the larynx dorsally and caudally.
3-The occiptohyoideus muscle: is a smaller triangular muscle, which lies in the space between
the jugular process and stylohyoid bone.
Origin: the jugular process of the occipital bone.
Insertion: the dorsa extremity and ventral edge of the stylohyoid bone
Action: it carries the ventral extremity of the thyroid bone caudally.
4-The geniohyoideus muscle: is long spindle shaped muscle, which lies under the tongue.
Origin: medial surface of the molar part of the mandible close to the symphysis.
Insertion: the extremity of lingual process of the hyoid bone.
Action: it draws the hyoid bone and tongue rostrally.
5-The ceratohyoideus muscle: a small triangular muscle lays in the space between the
thyrohyoid and ceratohyoid bones, under cover the hypoglosseus.
Origin: the caudal edge of the ceratohyoid bone and ventral border of the stylohyoid bone.
Insertion: the dorsal edge of the thyrohyoid bone. Action: it raises the thyrohyoid bone and the
larynx.
6-The hyoideus transversus muscle: is small unpaired muscle, which extends transversely
between the two ceratohyoid bones.
Origin: ceratohyoid bones. Insertion: thyrohyoid bone.
Action: when it contracts, it elevates the root of the tongue.
7-The sternothyrohyoideus muscle: is long, slender and digastrics muscle applied to the ventral
surface of the trachea.
Origin: the cartilage of manubrium.
Insertion: the basihyoid bone and lingual process of the hyoid bone.
Action: to retract and depress the hyoid bone, the base of tongue and the larynx.
8-The omohyoideus muscle: is thin, ribbon like.
Origin: the sub scapular fascia close to the shoulder joint.
Insertion: the basihyoid bone and lingual process of the hyoid bone.
Action: to tact the hyoid bone and the root of the tongue.
Muscles of mastication (mandibular muscle):
The muscles of this group are six in number in the horse, they are extending from the maxilla and
the cranium, and are all inserted into mandible.
1-The masseter muscle: it is semi-elliptical in out line.
Origin: zygomatic arch and facial crest. Insertion: lateral surface of the ramus of the mandible.
Action: to bring the jaws together.
2-The temporal muscle: Occupies the temporal fosse.
Origin: the temporal fosse Insertion: the coroniod process of the mandible. Action: raise the
mandible.
3-Pterygoidus medialis muscle: occupies the medial surface of the ramus of the mandible similar
to that of the masseter laterally.
Origin: the crest formed by the pterygoid process of the basisphenoid and palatine bone.
Insertion: medial surface of the ramus of the mandible. Action: to raise the mandible.
4- Pterygoidus lateralis muscle: is similar than the preceding one .it is situated lateral to its
dorsal part.
Origin: the lateral surface of pterygoid process of the basisphenoid bone.
Insertion: the mandible. Action: to draw the mandible rostrally.
5-The digastricus muscle: is composed of two fusiform flattened bellies united by round tendon.
The occiptomandibular part of the caudal belly extends from jugular process of occipital bone to
the caudal border of the mandible. It covered by parotid gland.
Origin: jugular process of occipital bone.
Insertion: medial surface of the ventral border of molar part of mandible.
Action: it assists in depressing the mandible and opening mouth.