MYOLOGY OF THE LANIPEKUN, D. O.

Dept. of Veterinary Anatomy,

HEAD University of Ibadan.

14 November, 2024
MUSCLES OF THE HEAD
These are grouped into 6 classes
On the basis of innervation & embryonic origin
These include-
1. Extrinsic ocular muscles
2. Mandibular muscles (V3)
3. Facial expression muscles (VII)
4. Pharyngeal muscles
5. Laryngeal/Hyoid muscles
6. Extrinsic lingual muscles
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**CUTANEUS MUSCLES
Platysma- Cutaneus faciei & Cutaneus colli
 Cutaneus trunci
 Cutaneus omobrachialis
 Preputial muscles

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CUTANEUS MUSCLE
 FRONTALIS- forms the rostral part of the
cutaneus faciei; its fibers replace the levator anguli oculi
medialis (corrugator supercilii)
Origin: The base of the horn & intercornual
protuberance
Insertion: The fibers run rostrally toward the sup.
palp.; spread out in the forehead & around orbicularis
oculi
Action: To wrinkle the skin of the forehead; elevate
the sup. palp.
Blood supply: Supraorbital artery
Nerve supply: The facial nerve

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 MUSCLES OF FACIAL
EXPRESSION
These are seen around the muzzle,
nostrils, lips and cheeks of the animal-
Caninus (Dilator naris lateralis) Depressor labii mandibularis (inferioris)
Dilator naris apicalis Orbicularis oris
Levator nasolabialis Buccinator
Levator labii maxillaris (superioris) Zygomaticus
Depressor labii maxillaris (superioris) Malaris

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1. LEVATOR NASOLABIALIS- is an extensive but thin
muscle which merges with the frontalis; divides into deep &
superficial layers, though dorsal to the caninus & LLM in the ox
but remains undivided in the small ruminant [in the goat]
Origin: The rostral part of frontal bone & frontalis
Insertion: The nostril and the max. lip (supf.); the nasal process of
incisive & lateral nasal cartilages (deep)
Action: To elevate the max. lip; dilate the nostrils
Blood supply: Facial & maxillary labial artery
Nerve supply: Branches of facial nerve

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2. LEVATOR LABII MAXILLARIS- blends with the fibers of
caninus at its origin but separates as they course rostrad; possesses
tendinous insertions
Origin: The facial tuber
Insertion: The central part of the max. lip and muzzle by flat tendons
Action: To elevate the max. lip & muzzle
Blood supply: Maxillary labial artery
Nerve supply: Branches of facial nerve

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3. CANINUS- located between LLM and DLM; formerly Dilator
naris lateralis and its fibers pass through the two parts of the
levator nasolabialis
Origin: The facial tuber of the ?????
Insertion: The lateral wall of the nostril
Action: To pull the lateral wall of the nostril caudally (dilation)
Blood supply: Maxillary labial artery
Nerve supply: The facial nerve

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4. DEPRESSOR LABII MAXILLARIS- is the most ventral
of the three muscles that extend rostrally from the facial tuber
Origin: The maxilla & facial tuber
Insertion: The max. lip and ventral aspects of the nares
Action: To depress the rostral part of the max. lip & ventrolateral
portions of the nares
Blood supply: Maxillary labial artery
Nerve supply: Branches of facial nerve

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9 November 2024 10
5. DILATOR NARIS APICALIS- located beneath the pad of
the nasolabial gland of the muzzle; formerly Transversus nasi
Origin: The free border and dorsal surface of the body of incisive
Insertion: The medial and ventral portions of the nostril
Action: To dilate the nostrils
Blood supply: Nasolabial artery of the palatine
Nerve supply: The facial nerve

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6. DEPRESSOR LABII MANDIBULARIS- is a thin muscle
and the most ventral of the muscles of facial expression
Origin: The caudal alveolar border of the mandible & masseteric fascia
Insertion: The mand. lip and the skin of the area
Action: To depress the mand. lip & surrounding skin
Blood supply: Mandibular labial artery
Nerve supply: Branches of facial nerve

DEPRESSOR LABII MANDIBULARIS

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7. ORBICULARIS ORIS- is situated between the skin (supf.) and
the mucous membrane (deep); forms a sphincter of the lips
(incomplete in the ox but complete in small rum’t)
Action: To close the lips (rima oris)
Blood supply: Maxillary labial & mental arteries
Nerve supply: Branches of facial nerve

ORBICULARIS ORIS

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8. BUCCINATOR- is a broad, flat muscle which forms the major
portion of the cheek; extends from the labial commissure to occupy the
buccal region between the maxilla & mandible (pars molaris et buccalis)
Origin: The alveolar border of the maxilla & from the oral commissure
to the mandibular ramus
Insertion: Most fibers blend with orbicularis oris; others are unspecific
Action: To retract the commissure & flatten the cheek; assist in mastication
Blood supply: Maxillary, mandibular labial & buccal arteries
Nerve supply: Facial nerve

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9. ZYGOMATICUS- is a strong band of muscle extending from the
zygomatic arch (on the bone itself via a tendon in small rum’t) across the
buccinator
Origin: The masseteric fascia & temporal process of zygomatic bone
Insertion: Angle of the lip & blends with the orbicularis oris
Action: To retract the commissure of the lip
Blood supply: Facial artery
Nerve supply: Facial nerve

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9 November 2024 16
10. MALARIS- is a broad, thin muscle that spreads out on the fascia over
the buccinator & masseter; situated ventral & rostral to the medial angle
of the eye (**has 2 parts- levator buccalis & depressor palp. inferioris)
Origin: The facial part of the lacrimal bone
Insertion: The buccal fascia around the dorsal part of the buccinator
Action: To elevate the caudal part of the cheek via its contraction
Blood supply: Malar artery
Nerve supply: Facial nerve

**some authors’ opinion

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MUSCLES OF MASTICATION
These are the muscles that receive their motor innervation via the
mandibular branch of the CN V and they include-
Masseter
Temporalis
Pterygoideus medialis
Pterygoideus lateralis
Digastricus

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1. MASSETER- is a broad, strong & flat muscle located on the lateral
surface of the mandible; separated into 2 layers in the ox & goat but 3 in
the sheep. A tendinous muscle.
Origin: The facial tuber; the ventral surface of zygomatic arch
Insertion: The mandibular angle; lateral surface of the mandibular ramus
Action: To close the jaw and move the mandible rostrad
Blood supply: Facial, transverse facial & masseter arteries
Nerve supply: Masseter nerve

9 November 2024 19
MASSETER
9 November 2024 20
2. TEMPORALIS- is a lateral muscle that completely fills the temporal
fossa; it is not as well developed in ruminants as in carnivores
Origin: The temporal fossa
Insertion: The coronoid process and its surfaces
Action: To retract & raise the mandible; aid to clench the teeth
Blood supply: Branches of the deep temporal artery
Nerve supply: Deep temporal nerve of CN V

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TEMPORALIS

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3. PTERYGOIDEUS MEDIALIS- is a fan-shaped muscle, with its
fibers directed ventrad & caudad; its medial face appears tendinous
Origin: The lateral surface of the perpendicular part of palatine &
pterygoid process of basisphenoid
Insertion: The medial surface of the mandible, ventral & caudal to the ‘MF’
Action: To raise & close the jaws
Blood supply: Pterygoid branches from the maxillary artery
Nerve supply: Medial pterygoid nerve of CN V

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4. PTERYGOIDEUS LATERALIS- is a wide and thin rostrally but
thick and narrow caudally; it is partly covered by the preceding muscle
Origin: The pterygopalatine fossa & pterygoid process of basisphenoid
Insertion: The rostromedial of the mandibular condyle & the neck
Action: To move the mandible rostrad (acting together); lateral mov’t (singly)
Blood supply: Pterygoid branch from the maxillary artery
Nerve supply: Lateral pterygoid nerve of CN V

9 November 2024 24
PTERYGOIDEUS MUSCLES

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5. DIGASTRICUS- possesses “2 bellies” (rostral/caudal), hence its name;
an intermediate tendon separates the bellies
Origin: Via tendons from the jugular (paracondylar) processes of occipital
Insertion: The medial surface of the body of the mandible
Action: To depress the mandible & open the mouth
Blood supply: Facial artery
Nerve supply: The mylohyoid & facial nerves

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DIGASTRICUS

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REFERENCES
1. Dyce, K. M and Wensing, C. J. G. (2010). Textbook of Veterinary Anatomy. 4th Ed.
2. http://ecoursesonline.iasri.res.in
3. Sisson, S and Grossman, J. D. (1975). Anatomy of Domestic Animals. 5th Ed.

9 November 2024 28
 THANK YOU
FOR
LISTENING
9 November 2024 29
ANATOMY OF THE EYE
& OCULAR ADNEXA
(VAN IV)
LANIPEKUN, D. O.
DEPT. OF VETERINARY ANATOMY,
UNIVERSITY OF IBADAN.
22 FEBRUARY, 2024
 2
INTRODUCTION

The Eye, an organ of vision, consists of-

 The Eyeball
 The Lacrimal apparatus
 The Conjunctiva
 The Palpebrae
 The Ocular muscles & orbital fasciae
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THE ORBIT

 This is a cone-shaped cavity on the lateral part of the skull

(frontal, lacrimal, zygomatic, maxilla, palatine & sphenoid)
 The margin of the “cone” is incomplete laterally in carnivores and
pig- completed by the orbital ligament
 In the domestic mammals, the lateral and ventral parts of the orbit
are formed by the fibrous periorbita

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THE ORBITAL FASCIAE

These form concentric layers around the

eyeball and arranged from without within
as-
 Periorbita
 Superficial muscular fascia
 Deep muscular fascia

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THE ORBITAL FASCIAE- Periorbita

 The periorbita is attached near the optic foramen at the apex of the cone
and blends with the periosteum at the orbital margin and on the medial and
dorsal walls of the orbit
 Laterally and ventrally, it is unattached and separates the orbital structures from
its surrounding extraorbital tissues
 The periorbita splits at the orbital margin-
 As the periosteum of the facial bones;
 As the orbital septum, which forms part of the palpebral tarsal plate
3/1/2024
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THE ORBITAL FASCIAE- Supf. & Deep Fasciae

 The superficial muscular fascia lies just within the periorbita,

being loose and envelops the levator palpebrae superioris (LPS) and the
lacrimal gland
 The deep muscular fascia is more fibrous; it arises from the
eyelids and from the limbus of the eyeball, which it closely invests.
It is reflected around the muscles attaching to the eyeball,
providing each (and also the optic nerve) with a fascial envelope
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THE OCULAR MUSCLES

 These are grouped as-

 Intrinsic
 Extrinsic
 The extrinsic ocular muscles function to move the eyeball and are 7-
 Rectus dorsalis  Retractor bulbi
 Rectus ventralis  Dorsal oblique
 Rectus medialis  Ventral oblique
 Rectus lateralis
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 10
RECTI MUSCLES

The straight muscles are named according to their position

• Dorsal, Ventral, Lateral & Medial
 They also named based on their action as levator, depressor,
abductor and adductor oculi
 O: flat muscular bands arise around the optic foramen,
diverge and pass along the corresponding aspects of the
eye-ball forward
 I: terminate in fine aponeurotic tendons to be inserted to
the fore part of the sclera in front of the equator
 A: EDA2
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 11
OBLIQUE MUSCLES

The oblique muscles are two- Dorsal & Ventral

 The DO is long and differs from others in having an interrupted
course; VO is more direct & muscular
 O: DO arises from the ethmoidal foramen and passes forward along
the internal wall of the orbit, lying medial to the MR and gains at the
level of supraorbital process, a fibro-cartilaginous pulley. It then
reflects around this pulley outwards and forwards and passes
between the eyeball and DR; VO arises from the depression behind
the lacrimal fossa, curves around the VR
 I: DO terminates between the dorsal and lateral recti about half an
inch behind the margin of the cornea; VO inserts into the sclera near
and partly beneath the lateral rectus
 A: ER-DR ELEVATE AND ROTATE - DEPRESS AND
ROTATE
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RETRACTOR BULBI

The RB is enclosed within the recti muscles, envelops the

optic nerve with its bundles alternating with the recti
 O: four bundles which arise around the optic foramen
 I: the posterior part of the sclera behind the recti
 A: Retracts the eyeball into the orbit

 BS: Ophthalmic aa.

 NS: Do4LrRb6Rest3 dorsal oblique CN IV
Lateral rectus retractor bulbi CN VI
Other extrinsic muscle CN III
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 13
THE EYELIDS (PALPEBRAE)

 The eyelids control the entrance into the orbit & protect the eyeball from desiccation
via tear distribution
 They are two; described as superior palpebra (upper) & inferior palpebra (lower)
 The lid has an outer skin, middle muscle & CT, and inner conjunctiva
 A dense fibrous plate with glandular core supporting the margin of the eyelid- TARSUS
 Meibomian (Tarsal) glands open into the margin of the eyelid
 Special hairs associated with the margins are known as CILIA (longer & plenty on the SP)
 Other glands found in the eyelid include- sudoriferous & sebaceous glands
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3/1/2024
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THE PALPEBRAE & MUSCULATURE

 Palpebral Fissure- is described as the elliptical space between the two eyelids
 The ends of the fissure are referred to as Angles/Canthi (sing- canthus)
 The point of junction between the upper & lower lids is the commissure
 The Palpebral Musculature- classified to function in opening or closure of the lid
 Orbicularis oculi- closure of eyelids
FACIAL NERVE
 Frontalis/Corrugator supercilii- LAOM: opening
paralysis????
 Malaris- depressor palpebrae inferioris: opening
 Levator palpebrae superioris- opening
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 16
THE THIRD EYELID/NICTITATING
MEMBRANE/PALPEBRA TERTIA
 It is situated at the medial canthus, formed from a T-
shaped cartilage covered by a loose “semilunar” fold of
conjunctiva (palp. & bulbar faces)
 The cartilage of the 3EL is embedded in fat and the
retraction of the eyeball causes it to move across to
protect the eyeball
 The cartilage is closely adherent to the gland tissue
which resembles the lacrimal gland
 Superficial gland- Nictitans gland
 Deep gland- Harderian gland (pig & cattle)
3/1/2024
 17
THE CONJUNCTIVA

 The conjunctiva attaches the palpebrae to the eyeball

as the mm. of the former
 It extends from the innermost face of the lid as palp.
conjunctiva, then reflects from both lids close to the
eyeball to form folds called fornices
 The conjunctiva continues from both sup. & inf.
fornices to the limbus of the eyeball as the bulbar
conjunctiva
3/1/2024
 18
THE CONJUNCTIVA

 When the two lids are closed, the conjunctiva forms

a complete circle referred to as the conjunctival sac
 It gives a bright pinkish appearance when examined
in a healthy subject; gives a clue of the health status
 White- anaemia
 Red- fever/conjunctivitis
 Yellow- jaundice
 Blue- cyanosis
3/1/2024
 19
THE LACRIMAL APPARATUS

The lacrimal apparatus is composed of-

 The lacrimal gland, gland(s) of PT
 The excretory ducts (12-15)
 The lacrimal puncta (2)
 The lacrimal ducts/canaliculi (2)
 The lacrimal sac
 The nasolacrimal duct
**lacrimal caruncle
3/1/2024
 20
THE EYEBALL

The eyeball contains THREE concentric tunics-

 Outer fibrous tunic
 Middle vascular tunic
 Inner nervous tunic

1 March 2024
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FIBROUS TUNIC

This is the only complete tunic, forming a complete ring

It is composed of TWO parts-
 an anterior transparent avascular part called the CORNEA and
 a posterior opaque vascular part known as the SCLERA

1 March 2024
 22
CORNEA

1
 Forms the anterior of the fibrous tunic
5
 It is transparent, colorless, and avascular
 It has two surfaces-
 The anterior surface is convex and curved
 The posterior surface is concave and forms the
anterior boundary of the anterior chamber
 Its margin joins the sclera at the LIMBUS
1 March 2024
 23
CORNEA CONT’D

 Corneal epithelium lined by stratified squamous epithelium

 Lamina limitans anterior (Bowman’s membrane)- a very thin and
homogeneous membrane
 Substantia propria -lamellae of connective tissue with connective
tissue corpuscles
 Lamina elastica (Descemet’s membrane)- a thick, elastic
homogeneous membrane
 Endothelium- lines the cornea & reflected over the iris
 Blood??? & Nerve supply (corneal reflex) it lacks blood supply and get it by diffusion
Opthalmic part of trigeminal nerve
1 March 2024
optic nerve
 24
SCLERA
 The sclera is a dense white fibrous membrane
forming about four fifths of the fibrous tunic of
the eyeball
 It is thickest in the vicinity of the posterior pole,
thins at the equator and increases in thickness
toward the junction with the cornea
 It is the “white of the eye” although often
pigmented in some species
 Its external surface gives insertion to ocular muscles
and is covered in front by the bulbar conjunctiva
1 March 2024
 25
SCLERA
 The internal surface is attached to the choroid
coat by pigmented connective tissue
 The sclera here appears to form a bevel in which
the cornea is fixed & at the corneoscleral
junction, there is a circular venous plexus, the
plexus venosus sclerae (canal of Schlemm)
 The optic nerve pierces the posterior part of the
sclera a little below and lateral to the posterior
pole (in the postero-ventrolateral quadrant)
 Blood & Nerve supply (cilliary aa. & nn.) 1 March 2024
 26
VASCULAR TUNIC

It lies internal to the fibrous tunic and comprises

 an anterior IRIS,
 a middle CILIARY BODY and
 a posterior CHOROID

1 March 2024
 27
CHOROID
 It is a thin membrane lying between the sclera and retina
 The internal surface is in intimate contact with the pigmented layer of the retina
 The choroid is generally dark brown in colour but an extensive area above the level
of the optic papilla has a metallic lustre, the colour varying from iridescent blue to
green called the TAPETUM LUCIDUM (a nocturnal adaptation in some species)
 The “eyeshine effect” is the reflection of the tapetum in animals when they look
towards a light source in the dark
 The TL is cellular in carnivores but fibrous in ruminants & horses
 Absent in the porcine & primates
1 March 2024
28

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CILIARY BODY
 It is the middle part of the vascular tunic and connects the choroid with the
periphery of the iris
 It consists of three parts-
 Ciliary ring, Ciliary processes and Ciliary muscle
 The ciliary ring is continuous with the anterior part of the choroid and presents
on its inner surface, numerous fine ridges (ciliary processes) arranged in a radial
manner
 The ciliary processes extend numerous fibers, zonular fibers, to suspend the lens
 The ciliary muscles, a circular band of unstriped muscle, constitute the outer part
of the ciliary body and lies between the sclera and ciliary processes
 The contraction of the ciliary muscles aids in accommodation by altering the lens’
shape 1 March 2024
 30
IRIS (DIAPHRAGM)
 The innermost & smallest part of the vascular tunic, located between the lens
& cornea
 It is a muscular diaphragm pierced centrally by an elliptical opening, the Pupil
 The pupillary margin surrounds the pupil & the upper margin bears small
masses of pigmented tissue called corpora nigra or granula iridica (in the
ruminant & horse)
 The anterior surface is dark brown in colour and is lined by the reflection of
the corneal endothelium which forms the posterior boundary of the anterior
chamber
 The posterior surface (lined by endothelium) is dark and is in contact with the
lens but peripherally it is separated from it by an annular space called the
posterior chamber
 The anterior and posterior chambers communicate through the pupil and
contain aqueous humor 1 March 2024
 31
IRIS CONT’D

 The iris is chiefly composed of a framework of connective tissue called the Iridic stroma
containing numerous pigment cells
 The muscular tissue is unstriped and consists of a sphincter pupillae around the pupil and a
dilator pupillae with fibers radiating from the sphincter to the ciliary border
 The colour of the eye is determined by the pigmentation of the iridic stroma
 If it contains little pigment, the pigmented epithelium on the posterior surface shows through and gives a blue coloration
 In the cat, there is diffuse yellow pigmentation of the stromal cells and so the eye has a golden sheen; In albinos, the
pigment is absent here, as elsewhere, and the iris is pink is colour
 Iris angle (spaces of Fontana & canal of Schlemm-- IOP)
 Blood supply (C. aa.) Nerve supply (C. nn & ANS [CN V&III]) 1 March 2024
 32
NERVOUS TUNIC (RETINA)

 This layer contains the light-sensitive receptor cells as well as the sensory neurons; the retina is
actually an extension of the brain, and the connection is via the optic nerve
 The retina has 10 layers, the innermost (pigmented epithelium) closely adherent to the choroid
 Pigment cell layer  Inner nuclear layer
 Receptor (neuroepithelial) cell layer  Inner plexiform layer
 Outer limiting membrane  Ganglion cell layer
 Outer nuclear layer  Optic nerve fiber layer
 Outer plexiform layer  Inner limiting membrane

1 March 2024
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NERVOUS TUNIC (RETINA)

 The retina originates from the optic cup (2 layers) and lines the uvea till the pupillary margin
 Three (3) parts are identified-
 Pars optica retinae
 Pars ciliaris retinae
 Pars iridica retina
 Pars optica retinae- only about two-thirds of the retina is exposed to light from the pupil;
hence the receptor cell layer is not present in all the parts of the retina
 The optic disc is the area where the axons of the ganglion cells leave the retina and this disc
is devoid of photoreceptor cells- blind spot (seen just inferior to the tapetum)
 Area centralis retinae- similar to Macula, just around the tapetum; max. optical res. 1 March 2024
 34
REFERENCES

1. Dyce, K. M and Wensing, C. J. G. (2010). Textbook of Veterinary Anatomy. 4th Ed.

2. http://ecoursesonline.iasri.res.in
3. Sisson, S and Grossman, J. D. (1975). Anatomy of Domestic Animals. 5th Ed.

1 March 2024
THANK YOU
35

FOR
LISTENING
1 March 2024
 ANATOMY OF THE EAR
GROSS ANATOMY II
(VAN MODULE IV)

LANIPEKUN, D. O.
DEPARTMENT OF VETERINARY ANATOMY,
UNIVERSITY OF IBADAN
NOVEMBER 21, 2024
Wednesday, November 20, 2024 LANIPEKUN, D.O. 1
INTRODUCTION
• The ear is the organ of hearing and some aspects of
proprioception.
• It is divisible into three parts;
External ear
Middle ear (tympanic cavity)
Internal ear

Wednesday, November 20, 2024 LANIPEKUN, D.O. 2

1. EXTERNAL EAR
• It is also referred to as auris externa (Latin- auris)
• It comprises-
• Auricle or Pinna, and
• External acoustic meatus
• The auricle projects from the head and in domestic animals, unlike
man, can be turned in different positions without turning the head
(ear muscles)
• The external acoustic meatus (EAM) leads inward from the base of
the auricle and conduct vibrations to the tympanic cavity.
• The structure of the external ear is composed of cartilages, complex
arrangement of muscles and the skin
Wednesday, November 20, 2024 LANIPEKUN, D.O. 3
AURICLE/PINNA
• Cartilaginous funnel-shaped structure attached to the osseous
external acoustic meatus by its base to aid free movement
• Its long axis assumes varying positions in different species
• It has two (2) surfaces, borders and extremities
• Convex/dorsum and Concave/scapha
• Rostral (margo tragicus) and Caudal (margo antitragicus)
• Base and Apex
• Its framework is composed of cartilages (auricular, annular and
scutiform)

Wednesday, November 20, 2024 LANIPEKUN, D.O. 4

AURICLE/PINNA cont’d
• The auricular (conchal) cartilage gives the pinna its shape
• Most conspicuous of the ear cartilages
• Its base is concealed by the auricular muscles and parotid gland
• It continues with the annular cartilage medially towards the osseous EAM
• The annular cartilage is a quadrilateral curved plate
• It is in direct contact with the osseous EAM
• Together with the ventral portion of the auricular cartilage, it forms the
cartilaginous part of the EAM
• The scutiform cartilage is an irregular plate rostrodorsal to auricular
cartilage
• Its superficial face is slightly convex and its deep face is concave
• It moves freely over the underlying parts of the auricular cartilage and skull

Wednesday, November 20, 2024 LANIPEKUN, D.O. 5

 CARTILAGES OF THE PINNA

Wednesday, November 20, 2024 LANIPEKUN, D.O. 6

AURICULAR MUSCLES
• They are classified into two-
• Intrinsic
• Extrinsic

• INTRINSIC MUSCLES
a. Antitragicus
b. Helicis
c. Transversus & Obliqui auriculares

Wednesday, November 20, 2024 LANIPEKUN, D.O. 7

AURICULAR MUSCLES cont’d
• EXTRINSIC MUSCLES
a. ROSTRAL- Scutuloauricularis supf., Scutuloauricularis profundi
(major & minor), Frontoscutularis, Zygomaticoauricularis
b. CAUDAL- Cervicoscutularis, Cervicoauricularis supf.,
Cervicoauricularis medius, Cervicoauricularis profundus
c. VENTRAL- Parotidoauricularis
d. DORSAL- Interscutularis, Parietoauricularis

Wednesday, November 20, 2024 LANIPEKUN, D.O. 8

Wednesday, November 20, 2024 LANIPEKUN, D.O. 9
AURICULAR SKIN
• Both surfaces of the pinna possess skin;
• Concave surface has darker skin and intimately adherent to the
cartilage
• Convex surface skin possesses no special feature
• There are some cutaneous ridges which run parallel to the borders
of the auricular cartilage
• Within the initial part of the EAM, the skin is thin and contains
abundant large, coiled ceruminous glands (cerumen- ear wax),
sparsely covered with fine hairs

Wednesday, November 20, 2024 LANIPEKUN, D.O. 10

EXTERNAL ACOUSTIC MEATUS
• Connects the passage at the base of the auricular cartilage to
the tympanic membrane
• It is directed medially, ventrally and rostrally from the conchal
cavity
• It consists of two portions;
• Cartilaginous part- formed by the ventral part of auricular cartilage
and the annular cartilage
• Osseous part- formed within the temporal bone

Wednesday, November 20, 2024 LANIPEKUN, D.O. 11

2. MIDDLE EAR
• It is also referred to as auris media (cavum tympani)
• This is an irregular space within the temporal bone that is filled with air
• Air passes from the nasal part of the pharynx through the auditory tube
• There is a chain of three tiny movable bones
• Convey the vibration from the external ear to the tympanic membrane across
the cavity to the internal ear.
• Serves as nexus for the nasopharynx, external and internal ears
• The mucous membrane of the tympanic cavity is continuous with that
of the pharynx through the auditory tube
• It invests the auditory ossicles, the muscles and nerves & forms the medial layer
of the tympanic membrane
Wednesday, November 20, 2024 LANIPEKUN, D.O. 12
2. MIDDLE EAR
• It comprises-
• Tympanic membrane/cavity
• Auditory ossicles, chorda tympani nerve and associated muscles
• Auditory (Eustachian) tube
• The tympanic cavity is divided into 3 communicating compartments;
• Epitympanicum (houses a part of the auditory ossicles and CT)
• Mesotympanicum (main tympanic cavity- OW, RW & other parts of the ossicles)
• Hypotympanicum (tympanic bulla)

Wednesday, November 20, 2024 LANIPEKUN, D.O. 13

MIDDLE EAR cont’d

Wednesday, November 20, 2024 LANIPEKUN, D.O. 14

 TYMPANIC MEMBRANE
• It is a membranous lining which extends from
the margin of the tympanic incisures to the main
tympanic cavity
• Has two (2) parts- pars tensa & pars flaccida
• Has two (2) surfaces- medial convex (contacts the
manubrium of malleus) & lateral concave
• A depression on the lateral surface where the
malleus terminates- umbo membranae tympani
• Malleus appears like dorsocaudal light streak
during otoscopic exam of the membrane- stria
mallearis (labelled 1 in the upper right image)

Wednesday, November 20, 2024 LANIPEKUN, D.O. 15

AUDITORY OSSICLES
• The malleus, so named from its fancied
resemblance to a hammer, is attached to
the tympanic membrane. It consists of
head, neck and manubrium (handle)
• The incus, from its resemblance to an
anvil, but it is more like a premolar tooth
with two roots, which differ in length and
are widely separated from each other. The
incus is located between and connect to
the malleus and stapes by delicate
articulations. It consists of a body and two
crura- short and long
• The stapes, so called from its resemblance
to a stirrup, consists of a head, neck, two
crura and a base, and is attached to the
vestibular window

Wednesday, November 20, 2024 LANIPEKUN, D.O. 16

AUDITORY TUBE
• Extend from the tympanic cavity to the pharynx
• Transmit air to the tympanic cavity to equalize pressure on the surfaces of
tympanic membrane
OTHER STRUCTURES-
• Oval window
• Round window
• Ossicles muscles
• Stapedius (CN VII)
• Tensor tympani (CN V3)

Wednesday, November 20, 2024 LANIPEKUN, D.O. 17

 INTERNAL EAR
• It is also referred to as auris interna
• It is called the LABYRINTH because of the complexity of its shape; it
consists of two parts-
1. The osseous labyrinth, a series of cavities within the petrous part of the
temporal bone
2. The membranous labyrinth, a series of communicating membranous sac
and ducts contained within the bony cavities
• The osseous labyrinth consists of three parts;
 Semicircular canals (caudal)
 The vestibule (middle)
 Cochlea (cranial)

Wednesday, November 20, 2024 LANIPEKUN, D.O. 18

 THE LABYRINTHS OF THE INTERNAL EAR

Wednesday, November 20, 2024 LANIPEKUN, D.O. 19

SEMICIRCULAR CANALS-
• Located caudodorsal to the vestibule and
are three in number;
a) Cranial
b) Lateral
c) Caudal
• They are curved tubes placed at right
angles to each other and join with the
vestibule by 5 openings
• The cranial and caudal canals have a
common opening
• The terminal parts of the tube at their
junctions with the vestibule are dilated to
form Ampullae

Wednesday, November 20, 2024 LANIPEKUN, D.O. 20

THE VESTIBULE-
• A bony cavity placed medial to the tympanic cavity, continuous with the
cochlea cranially and semicircular canals caudally
• The oval window is situated at the lateral wall; medial wall is perforated
for the passage of the filaments of vestibulocochlear nerve and aqueduct
of vestibule (through the petrous temporal bone)
• The cavity of the vestibule lodges the UTRICLE and SACCULE of
membranous labyrinth
• These cavities contain a clear fluid, the PERILYMPH, in which the
membranous labyrinth is suspended

Wednesday, November 20, 2024 LANIPEKUN, D.O. 21

THE VESTIBULE cont’d

Wednesday, November 20, 2024 LANIPEKUN, D.O. 22

THE COCHLEA-
• A bony spiral canal winds two and a half turn around an osseous
central column, MODIOLUS, and has an appearance of a shell of a
snail.
• The osseous spiral lamina projects from the modiolus into the
cochlear and divides it into upper chamber, scala vestibuli (SV) and a
lower chamber, scala tympani (ST)
• SV begins in the vestibule and ST ends at the cochlear (round) window
• The two scalae communicate via the helicotrema at the cochlear apex
• The base of the cone formed by the cochlea is the cranial part of the
fundus of the internal acoustic meatus

Wednesday, November 20, 2024 LANIPEKUN, D.O. 23

THE COCHLEA cont’d

Wednesday, November 20, 2024 LANIPEKUN, D.O. 24

THE MEMBRANOUS LABYRINTH
• This is lodged within the bony cavities of the osseous
labyrinth; it is however, considerably smaller and is partly
separated from the bony walls by a fluid, the perilymph
• The membranous labyrinth contains fluid, the ENDOLYMPH
• it consists of FOUR divisions-
 Utricle and Saccule (both within the vestibule)
 Semicircular ducts
 Cochlear duct

Wednesday, November 20, 2024 LANIPEKUN, D.O. 25

THE MEMBRANOUS LABYRINTH cont’d

Wednesday, November 20, 2024 LANIPEKUN, D.O. 26

STRUCTURES IN MEMBRANOUS LABYRINTH
• The MACULAE- vestibular apparatus for static equilibrium
• The CRISTAE AMPULLARES- vestibular apparatus for dynamic equilibrium
• The SPIRAL ORGAN (of CORTI)- auditory apparatus

Wednesday, November 20, 2024 LANIPEKUN, D.O. 27

MEMBRANOUS LABYRINTH- Macula & Crista

Wednesday, November 20, 2024 LANIPEKUN, D.O. 28

MEMBRANOUS LABYRINTH- Organ of Corti

Wednesday, November 20, 2024 LANIPEKUN, D.O. 29

REFERENCES
• Dyce, K.M and Wensing, C.J.G. (2010). Textbook of Veterinary Anatomy,
4th Ed.
• Pasquini, C., Spurgeon, T and Pasquini, S. (1997). Anatomy of Domestic
Animals, systemic & regional approach. 9th Ed.
• Sisson, S and Grossman, J. D. (1975). Anatomy of Domestic Animals.
5th Ed.

Wednesday, November 20, 2024 LANIPEKUN, D.O. 30

 THANK YOU FOR
LISTENING

Wednesday, November 20, 2024 LANIPEKUN, D.O. 31

OSTEOLOGY AND MYOLOGY
OF THE NECK
GROSS ANATOMY II
(VAN MODULE IV)

LANIPEKUN, D. O.
DEPARTMENT OF VETERINARY ANATOMY,
UNIVERSITY OF IBADAN
4 JANUARY, 2024
OSTEOLOGY OF THE NECK
• The neck connects the head with the trunk
• The core structures of the neck—the cervical vertebrae and the associated muscles.
• Cervical vertebrae are the main skeletal component of the neck.
• Usually 7 in most mammals.
• C1-C2 are atypical and modified for movement between the articulating
bones (Atlas and Axis).
• C3-C7 are referred to as typical cervical due to their features

• REVIEW THE BONES OF THE CERVICAL SERIES

Wednesday, February 14, 2024 Lanipekun D. O. 2
• The -
• Lacks a transverse foramen
• The dorsal arch bears a large dorsal tubercle and the ventral arch, a large ventral
tubercle, which is sometimes bifid
• The -
• Its cranial extremity bears the dens
• Its spinous process is a high and straight crest (not split caudally as in the horse)
• The lateral vertebral foramen is large (absent in the dog)
-
• The spinous process is long and inclined cranially.
• Only on the seventh is it almost vertical
• On the first, the spinous process is represented by a tubercle
• The transverse process of C3-C5 bears a cranial ventral tubercle and a
caudal dorsal tubercle
• On C6, the ventral tubercle is replaced by a sagittal quadrilateral plate, the ventral
lamina.
• The cranial and caudal articular processes are small.
Wednesday, February 14, 2024 Lanipekun D. O. 3
Wednesday, February 14, 2024 Lanipekun D. O. 4
MYOLOGY OF THE NECK
• For ease of description, muscles of the neck can be grouped based on
their relation to the cervical vertebrae.
1. VENTRAL CERVICAL MUSCLES

2. DORSOLATERAL CERVICAL MUSCLES

• Ventral part of the neck is a region of considerable clinical importance

as a result of the vital structures that traverse it en route between the
head and thorax.
• These structures occupy a CENTRAL VISCERAL SPACE
Wednesday, February 14, 2024 Lanipekun D. O. 5
MYOLOGY OF THE NECK cont’d
• VENTRAL CERVICAL MUSCLES- these include
i. Sternocephalicus (sternomastoideus and sternomandibularis)
ii. Sternothyrohyoideus (combined sternothyroideus and sternohyoideus)
iii. Omohyoideus
iv. Scaleni
v. Rectus capitis ventralis
vi. Rectus capitis lateralis
vii. Longus colli
viii. Longus capitis
ix. Intertransversarii
NOTE: The central visceral space is bounded by
majority of the ventral cervical muscles.
Wednesday, February 14, 2024 Lanipekun D. O. 6
MYOLOGY OF THE NECK cont’d
• DORSOLATERAL CERVICAL MUSCLES- comprise of
i. Rectus capitis dorsalis major
ii. Rectus capitis dorsalis minor
iii. Obliquus capitis cranialis
iv. Obliquus capitis caudalis
v. Splenius
vi. **Longissimus complex

Wednesday, February 14, 2024 Lanipekun D. O. 7

VENTRAL CERVICAL MUSCLES
1. Sternocephalicus- has 2 parts, superficial sternomandibularis and
deep sternomastoideus.
• Origin: both parts attach to the manubrium of the sternum and the 1st costal
cartilage.
• Insertion: sternomandibularis- ventral border of the mandible
sternomastoideus- mastoid process of the temporal bone
• Action: flexion of head and neck; acting singly to turn the head sideways
• Blood supply: common carotid arteries
• Nerve supply: ventral branches of cervical nerves

Wednesday, February 14, 2024 Lanipekun D. O. 8

VENTRAL CERVICAL MUSCLES cont’d
2. Sternothyrohyoideus- combined sternothyroideus and
sternohyoideus; seen on the ventral surface of the trachea.
• Origin: the cartilage of the manubrium of the sternum.
• Insertion: sternothyroideus- lateral surface of the lamina of thyroid cartilage
sternohyoideus- basihyoid bone, medial to omohyoideus’ insertion
• Action: retracts the hyoid bone, tongue and larynx; aids in deglutition
• Blood supply: muscular branches of common carotid arteries
• Nerve supply: ventral branches of 2 or 3 cervical nerves

Wednesday, February 14, 2024 Lanipekun D. O. 9

Wednesday, February 14, 2024 Lanipekun D. O. 10
Wednesday, February 14, 2024 Lanipekun D. O. 11
Wednesday, February 14, 2024 Lanipekun D. O. 12
3. Omohyoideus- it is quite reduced in the ruminants being covered by
the sternocephalicus and brachiocephalicus. It passes obliquely
across the trachea and thyroid cartilage to join the sternohyoideus
to the basihyoid bone.
• Origin: the transverse process of C3 and C4 by means of deep fascia
• Insertion: the basihyoid bone
• Action: to retract and raise the hyoid bone, thus retracting the root of the
tongue
• Blood supply: cranial thyroid arteries
• Nerve supply: the 2nd cervical nerves

Wednesday, February 14, 2024 Lanipekun D. O. 13

4. Scaleni- usually two; scalenus ventralis and scalenus dorsalis
(absent in the sheep).
• Origin: scalenus ventralis- the transverse processes of C3-C7
scalenus dorsalis- the transverse processes of C4-C6
• Insertion: scalenus ventralis- on the 1st rib
scalenus dorsalis- to the 2nd rib in the goat; 4th in the ox
• Action: to flex the neck laterad acting together or singly; pulling the ribs
craniad (respiratory) if the neck is fixed.
• Blood supply: vertebral and dorsal intercostal arteries
• Nerve supply: ventral branches of the cervical nerves

Wednesday, February 14, 2024 Lanipekun D. O. 14

Wednesday, February 14, 2024 Lanipekun D. O. 15
5. Rectus capitis ventralis- crosses the lateral aspect of the ventral
surface of the atlantooccipital joint. Formerly called rectus capitis
ventralis minor.
• Origin: ventral arch of the atlas
• Insertion: basilar part of the occipital bone, close to the insertion of longus
capitis
• Action: to flex the atlantooccipital joint
• Blood supply: occipital arteries
• Nerve supply: ventral branch of the 1st cervical nerve

Wednesday, February 14, 2024 Lanipekun D. O. 16

6. Rectus capitis lateralis- lies under the obliquus capitis cranialis. It
runs from the ventral arch and ventral surface of the wing of the
atlas to the occipital bone.
• Origin: the atlas
• Insertion: medial surface of the jugular process of the occipital bone, as well
as muscular tubercles on the same bone
• Action: to flex the atlantooccipital joint and to turn the head obliquely
• Blood supply: occipital arteries
• Nerve supply: ventral branch of the 1st cervical nerve

Wednesday, February 14, 2024 Lanipekun D. O. 17

Wednesday, February 14, 2024 Lanipekun D. O. 18
7. Longus colli- lies on the ventral surface of the cervical as well as
first 5-6 thoracic vertebrae. It thus has cervical and thoracic
portions.
• Origin: the bodies of the T1-T6 and the ventral surfaces of the transverse
processes of the cervical vertebrae, except the atlas
• Insertion: the thoracic part- the bodies and transverse processes of C6-C7,
the cervical part- the bodies of C1-C7; the ventral tubercle of C1
• Action: to flex the neck ventrally
• Blood supply: vertebral, common carotid, occipital and supreme intercostal
arteries; costocervical trunk
• Nerve supply: the ventral branches of the cervical nerves, except the first
the ventral branches of the first 4 or 5 thoracic nerves

Wednesday, February 14, 2024 Lanipekun D. O. 19

8. Longus capitis- the continuation of longus colli in the head region,
and also connecting the cervical part to the skull. Formerly called
rectus capitis ventralis major.
• Origin: on the (C2) C3-C6 transverse processes
• Insertion: muscular tubercles, between the basilar part of occipital and
basisphenoid bones
• Action: strong flexion of the atlantooccipital joint; a depressor of the head
• Blood supply: vertebral and occipital arteries
• Nerve supply: the ventral branches of the cervical nerves, from C2-C5

Wednesday, February 14, 2024 Lanipekun D. O. 20

Wednesday, February 14, 2024 Lanipekun D. O. 21
Wednesday, February 14, 2024 Lanipekun D. O. 22
9. Intertransversarii- occupy the spaces between the transverse and
articular processes on the lateral surfaces of C1-C7.
• Action: to flex the neck laterally
• Blood supply: vertebral arteries
• Nerve supply: the ventral branches of the cervical nerves

Wednesday, February 14, 2024 Lanipekun D. O. 23

CENTRAL VISCERAL SPACE
• The visceral space of the neck is enclosed by and
muscles.
• SUPERFICIAL MUSCLES
• The sternohyoideus ventral to the trachea
• The sternothyroideus, also thin and strap-like, lies lateral to the trachea
• These are the only structures that intervene between the larynx and trachea in the
cranial half of the neck.
• The preceding muscles are covered by the sternocephalicus in the caudal half.
• The brachiocephalicus dorsal to sternocephalicus forms the dorsolateral
boundary of the jugular furrow as well as the lateral superficial wall of the
visceral space.

Wednesday, February 14, 2024 Lanipekun D. O. 24

Wednesday, February 14, 2024 Lanipekun D. O. 25
CENTRAL VISCERAL SPACE cont’d
• DEEP MUSCLES
• The longus capitis ventrolateral to the body of cervical vertebrae
• The longus colli more medial than the longus capitis
• The scaleni are caudoventral to omohyoideus
• Omohyoideus is related to the medial faces of sternocephalicus and
brachiocephalicus.
• The fascia that covers these muscles ventrally detaches a superficial
leaf that encloses the many structures in the visceral space:
• The esophagus, trachea, thyroid and parathyroid glands, common carotid
arteries, vagosympathetic trunks, internal jugular veins, recurrent laryngeal
nerves and tracheal lymph nodes.

Wednesday, February 14, 2024 Lanipekun D. O. 26

DORSOLATERAL CERVICAL MUSCLES
1. Rectus capitis dorsalis major- has 2 parts,
superficial and deep.
• Origin: the spine of the axis
• Insertion: near the external occipital
protuberance of the occipital bone
• Action: to extend the head on the neck
• Blood supply: descending branch of the
vertebral artery
• Nerve supply: dorsal branch of the first cervical
nerve

Wednesday, February 14, 2024 Lanipekun D. O. 27

DORSOLATERAL CERVICAL MUSCLES cont’d
2. Rectus capitis dorsalis minor- lies under
the preceding. It sits between the atlas
and the occipital bone
• Origin: the dorsal arch of the atlas
• Insertion: near the external occipital
protuberance of the occipital bone
• Action: to extend the head on the neck
• Blood supply: descending branch of the
vertebral artery
• Nerve supply: dorsal branch of the first cervical
nerve
Wednesday, February 14, 2024 Lanipekun D. O. 28
 3. Obliquus capitis cranialis- strong
quadrilateral muscle which fills the
dorsolateral space between the atlas and
the occipital bone, covered by the
splenius and brachiocephalicus muscles
• Origin: cranial border and ventral face of atlas
wing
• Insertion: mastoid and jugular processes
• Action: to extend the head
• Blood supply: descending branch of the
vertebral artery
• Nerve supply: 1st cervical nerve

Wednesday, February 14, 2024 Lanipekun D. O. 29

4. Obliquus capitis caudalis- thick quadrilateral
muscle lying on the dorsolateral side of the
atlas and the axis
• Origin: lateral face of the spine and caudal
articular process of axis
• Insertion: dorsal surface of the wing of atlas
• Action: to extend or fix the atlantoaxial joint;
rotate the head and neck
• Blood supply: descending branch of the vertebral
artery
• Nerve supply: 2nd cervical nerve

Wednesday, February 14, 2024 Lanipekun D. O. 30

5. Splenius- thin, large, triangular muscle lying
on the dorsolateral side of the neck.
• Origin: spinous processes of T1-T4; aponeurotic
band to the nuchal ligament on C3
• Insertion: the wing of atlas; transverse processes
of C2-C5 (S. cervicis); occipital bone and mastoid
process of temporal bone
• Action: to elevate the head and neck
• Blood supply: deep cervical and descending
branch of the vertebral arteries
• Nerve supply: dorsal branches of cervical nerves
except the first two

Wednesday, February 14, 2024 Lanipekun D. O. 31

6. Longissimus capitis et atlantis- has 2 narrow bands extending
along the cervical vertebrae dorsal to the articular processes.
• Origin: transverse processes of T1-T7 and C5-C7; articular processes of C3-
C7
• Insertion: capitis- long tendon in common splenius to the mastoid process
atlantis- common tendon with splenius to the lateral border of
atlas
• Action: capitis- assist in extending the head on the neck
atlantis- lateral inclination of the neck
• Blood supply: deep cervical and vertebral arteries
• Nerve supply: dorsal branches of cervical nerves except the first two

Wednesday, February 14, 2024 Lanipekun D. O. 32

Longissimus capitis et atlantis

Thursday, February 15, 2024 Lanipekun D. O. 33

Wednesday, February 14, 2024 Lanipekun D. O. 34
REFERENCES
• Budras, K. D and Habel, R. E. (2003). Bovine Anatomy. 1st Ed.
• Dyce, K.M and Wensing, C.J.G. (2010). Textbook of Veterinary Anatomy,
4th Ed.
• Hale, W.G., Saunders, V.A and Margham, J.P. (2005). Collins Dictionary
of Biology, 3rd Ed.
• Pasquini, C., Spurgeon, T and Pasquini, S. (1997). Anatomy of Domestic
Animals, systemic & regional approach. 9th Ed.
• Sisson, S and Grossman, J. D. (1975). Anatomy of Domestic Animals.
5th Ed.

Wednesday, February 14, 2024 Lanipekun D. O. 35

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Wednesday, February 14, 2024 Lanipekun D. O. 36

 THANK YOU FOR
LISTENING

Wednesday, February 14, 2024 Lanipekun D. O. 37