Anatomy Of Tibia&Fibula

Note: All the notes provided us from gcvs 

recomended book Guide To The Dissection Of Dog By Howard E. Evans, PhD 

Lecture no 7

BONES OF THE PELVIC LIMB(continued)

Veterinary Anatomy  GCVS 1st semester

Tibia

The tibia the shin or leg bone, has a

proximal articular surface that flares out trans-versely and is also broad craniocaudally. It is wider

than the distal end of the femur, with which it

articulates, and is formed largely by two relatively

flat condyles. The medial condyleis separated

from the lateral condyleby the intercondylar em-inence.Both condyles include the articular areas

on their proximal surfaces and the adjacent nonar-ticular parts of the proximal extremity. The lateral

condyle is particularly prominent. It possesses a

facet on its lateral side for articulation with the

A B

Intercondylar eminence Cranial

intercondylar area

Medial condyle

Tibial tuberosity

Cranial border

Tibia

Medial malleolus

Extensor groove

Lateral condyle

Popliteal

sesamoid

Fibula

Head of fibula

Lateral malleolus

Caudal intercondylar area

Medial condyle

Popliteal notch

Tibia

A, Left tibia and fibula, cranial view. B, Articulated left tibia and fibula, caudal view.

Guide to the Dissection of the Dog 48

head of the fibula and provides origin for part of

the peroneus longus and cranial tibial muscles.

A sesamoid bone in the tendon of origin of the

popliteus (seen in radiographs) articulates with

the caudolateral condyle of the tibia. The semi-membranosus is inserted on the medial condyle.

Two biconcave fibrocartilages, the menisci,fill

part of the space between the apposed condyles

of the femur and tibia, making the joint congru-ent. The intercondylar eminenceconsists of two

small, elongated tubercles, which form its highest

part, and a shallow intercondylar area. The cranial

intercondylar areais a depression cranial to the

eminence and in large part between the condyles.

It affords attachment to the cranial parts of the me-nisci and the cranial cruciate ligament. The cau-dal intercondylar areaoccupies a place similar to

that of the cranial area but caudal to the eminence.

It provides attachment for the caudal part of the

medial meniscus. The popliteal notchis caudal

to the caudal intercondylar area and is located be-tween the two condyles. The popliteal vessels pass

through the notch. The tibial tuberosityis the

large quadrangular process on the proximocranial

surface of the tibia. The quadriceps femoris, the

biceps femoris, and the sartorius attach to this tu-berosity by means of the patella and patellar liga-ment. The tibial tuberosity is continued distally by

the cranial border of the tibia.It inclines laterally

on the body. The following muscles attach wholly

or in part to the cranial border of the tibia: biceps

femoris, semitendinosus, gracilis, and sartorius.

The extensor grooveis a small, smooth groove lo-cated at the junction of the lateral condyle and the

tibial tuberosity. The long digital extensor passes

through it.

The bodyis triangular proximally, nearly cylin-drical in the middle, and four sided distally. The

semitendinosus and gracilis are inserted on the

proximal medial surface. The proximal third of

the caudal surface serves for the insertion of the

popliteus medially and for the origins of the deep

digital flexor laterally.

The distal extremity of the tibia is quadrilat-eral in transverse section. The tibial cochlea,the

articular surface, consists of two grooves that

receive the ridges of the proximal trochlea of the

talus. The medial part of the distal extremity of

the tibia is the medial malleolus.The lateral sur-face of the distal extremity articulates with the

fibula by a small facet. No muscles arise from the

distal half of the tibia.

Fibula

The fibula has proximal and distal

extremities and an intermediate body.The proxi-mal extremity, or head,articulates with the lateral

condyle of the tibia. The distal extremity, the lateral

malleolus,has two grooves that contain the tendons

of the fibularis longus,fibularis brevis, and the lat- fibularis brevis, and the lat-  brevis, and the lat-eral digital extensor. These grooves redirect the force

of contraction. On the medial surface of the tibia is

a distinct facet for articulation with the distolateral

surface of the tibia and with the talus.

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Veterinary Dog Anatomy

Note: All the notes provided us from gcvs 

recomended book Guide To The Dissection Of Dog By Howard E. Evans, PhD 

Lecture no 6

BONES OF THE PELVIC LIMB(continued)

Veterinary Anatomy  GCVS 1st semester

Femur

The femur or thigh bone, is the

largest bone in the body. The flexor angle of the hip

is about 110 degrees. The flexor angle at the stifle is

from 130 to 135 degrees.

The femur is a typical long bone with a cylin-drical body and two expanded extremities. The

proximal extremity presents on its medial side a

smooth, nearly hemispherical head,most of which

is articular except for a small shallow fossa begin-ning near the middle of the head and usually ex-tending to its caudomedial margin. This fossa is

the fovea capitis femoris,to which the ligament

of the head of the femur attaches. The head is at-tached to the medial part of the proximal extrem-ity by the neckof the femur. The neck is distinct

but short and provides attachment for the joint

capsule. The greater trochanter,the largest emi-nence of the proximal extremity, is located directly

lateral to the head. To it attach the middle glu-teal and deep gluteal. The trochanteric fossais a

deep cavity medial to the greater trochanter. The

gemelli and the external and internal obturators

insert in this fossa. The lesser trochanter,a pyra-midal projection at the proximal end of the medial

side of the body of the femur, serves for the in-sertion of the iliopsoas. A ridge of bone extends

from the summit of the greater trochanter to the

lesser trochanter. This, the intertrochanteric crest,

represents the caudolateral boundary of the tro-chanteric fossa. The quadratus femoris inserts on

the crest at the level of the lesser trochanter. The

third trochanteris poorly developed. It appears at

the base of the greater trochanter as a small, rough

area on which the superficial gluteal inserts. The

third and lesser trochanters are located in about

the same transverse plane. The vastus parts of the

quadriceps femoris attach to the smooth proximal

cranial part of the femur. The bodyof the femur is slightly convex crani-ally. Viewed cranially, the body presents a smooth,

rounded surface. The caudal surface is rough and

is limited by medialand lateral lips.The lips,

closest together in the middle of the body, diverge

as they approach each extremity. The proximal

part of the medial lip ends in the lesser trochanter,

the distal part at the medial supracondylar tuber-osity. The proximal part of the lateral lip ends in

the third trochanter, the distal part at the lateral

supracondylar tuberosity. The adductor inserts on

most of the caudal rough surface, whereas a ten-don extends from the pectineus to the distal part

of the medial lip, where the semimembranosus

also attaches.

The distal extremity of the femur presents sev-eral articular surfaces. The trochlea,with ridges,

is the smooth groove on the craniodistal part of

the bone for articulation with the patella.The

medial trochlear ridge is usually thicker than the

lateral. The patella is a sesamoid in the tendon

of insertion of the large quadriceps femoris that

extends the stifle. It aids in the protection of the

tendon and the joint, but its chief purpose is re-direction of the tendon of insertion of the quad-riceps. The trochlea of the femur is continuous

with the condyles, which articulate, both directly

and through fibrocartilaginous menisci, with the

tibia. The medial and lateral condylesare sepa-rated from each other by the intercondylar fossa,

a deep, wide space. The two condyles are similar

in shape and surface area. Each is convex trans-versely and longitudinally. At the depth of the

intercondylar fossa the cruciate ligaments attach.

On the caudodorsal aspect of each femoral con-dyle is a facet on which a sesamoid bone (fabella) rests. The medial and lateral fabellae are in the

tendons of origin of the medial and lateral heads

of the gastrocnemius muscle. Proximal to these

sesamoid facets are the medial andlateral supra-condylar tuberositiesfrom which the gastrocne-mii arise. The superficial digital flexor also arises

from the lateral tuberosity. The popliteal surface

is a large, flat, triangular area on the caudal sur-face of the distal extremity proximal to the con-dyles and intercondylar fossa. The medial and

lateral epicondylesare rough areas on each side,

proximal to the condyles. They serve for the at-tachment of the collateral ligaments of the stifle.

The lateral epicondyle also gives rise to the pop-liteus. The small extensor fossais located on the

lateral epicondyle at the junction of the lateral

condyle and the lateral lip of the trochlea; from

it arises the long digital extensor. The semimem-branosus is inserted just proximal to the medial

epicondyle.

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Veterinary Dog Anatomy

Note: All the notes provided us from gcvs 

recomended book Guide To The Dissection Of Dog By Howard E. Evans, PhD 

Lecture no 5

BONES OF THE PELVIC LIMB

Veterinary Anatomy  GCVS 1st semester

BONES OF THE PELVIC LIMB

The pelvic girdle,or pelvis, of the dog consists

of two hip bones, which are united at the sym-physis pelvismidventrally and join the sacrum

dorsally. Each hip bone, or os coxae,is formed

by the  fusion of three primary bones and the

addition of a fourth in early life The

largest and most cranial of these is the ilium,

which articulates with the sacrum. The ischium

is the most caudal, whereas the pubisis located

ventromedial to the ilium and cranial to the large

obturator foramen. The acetabulum,a socket, is

formed where the three bones meet. It receives

the head of the femur in the formation of the hip

joint. The small  acetabular bone,which helps

form the acetabulum, is incorporated with the

ilium, ischium, and pubis when they fuse (about

the third month).

The pelvic canalis short ventrally but long

dorsally. Its lateral wall is composed of the ilium,

ischium, and pubis. Dorsolateral to the skeletal

part of the wall, the pelvic canal is bounded by

soft tissues. The pelvic inletis limited laterally

and ventrally by the arcuate line of the ilium.

Its dorsal boundary is the promontory of the sa-crum. The pelvic outletis bounded ventrally by

the ischiatic arch(the ischiatic arch is formed

by the concave caudal border of the two ischii);

mid-dorsally by the first caudal vertebra; and lat-erally by the superficial gluteal muscle, muscles

of the pelvic diaphragm, and the sacrotuberous

ligament.

Os Coxae

1. The iliuma flat

bone presenting two surfaces and three borders,

forms the cranial one half to three fifths of the

os coxae. It can be divided into a wide cranial

part, which is concave laterally and known as

the wing,and a narrow, laterally compressed

caudal part, the body.

The cranial border is arciform and usually

roughened and is more commonly known as the

iliac crest.It is thin but gradually increases in

thickness dorsally. The angle of junction of the

iliac crest with the ventral border is known as

the cranial ventral iliac spine, which provides a

place of origin for both bellies of the sartorius

and a part of the tensor fasciae latae. The tuber

coxaeis composed of the cranial ventral iliac

spine and the adjacent part of the ventral border

of the wing of the ilium. The rest of the ventral

border is concave. It ends in the lateral area for

the rectusfemoris just cranial to the

acetabulum.

The dorsal border of the ilium is broad and mas-sive. The junction of the dorsal border with the

iliac crest forms an obtuse angle that is a rounded

prominence, the cranial dorsal iliac spine.Cau-dal to the cranial dorsal iliac spine is the wide but

blunt caudal dorsal iliac spine.The two spines

and intervening bone make up the tuber sacrale,

which occupies nearly half the length of the dor-sal border of the ilium. The caudal half of the dor-sal border is gently concave. It forms the greater

ischiatic notchand also helps form the ischiatic

spine, which is dorsal to the acetabulum.

The external or gluteal surface(Fig. 2-33) of the

wing of the ilium is nearly flat caudally and con-cave cranially, where it is limited by the iliac crest.

The dorsal part of this concave area is bounded by

a heavy ridge, the tuber sacrale. The gluteal sur-face is rough ventrocranially. The middle gluteal

and a portion of the deep gluteal attach here.

The internal or sacropelvic surface(Fig. 2-34) of

the wing of the ilium presents a smooth, nearly flat

area that provides attachment for the iliocostalis, longissimus, and the quadratus  lumborum

muscles. The auricular surfaceis rough and ar-ticulates with a similar surface of the sacrum,

forming the sacroiliac joint. The arcuate lineis

located along the ventromedial edge of the sacro-pelvic surface of the body of the ilium and runs from

the auricular surface to the iliopubic eminence of

the pubis. The tendon of the psoas minor attaches

along the medial aspect of this line.

2. The ischium consists

of tuberosity, body, table, and ramus. It forms

the caudal part of the os coxae and enters into

the formation of the acetabulum, obturator fo-ramen, and symphysis pelvis. Its caudal border

consists of the ischiatic tuberosity laterally and

one half of the ischiatic arch medially. The ischi-atic tuberosityis the thick caudolateral margin

of the bone. The lateral angle of the tuber is en-larged and hooked; it furnishes attachment for

the sacrotuberous ligament. The medial angle

is rounded. The ventral surface is the place of

origin for the biceps femoris, semitendinosus,

and semimembranosus. The crus of the penis

and the muscle that surrounds it also attach to

the ischiatic tuberosity medially.

The body of the ischiumis the part lateral to the

obturator foramen. The ischiatic spineis a rounded

crest dorsal to the acetabulum, where the body of

ILIUM, ISCHIUM,

PUBIS

Hip

Coxa

FEMUR

Thigh

TIBIA, FIBULA

Leg

Crus

PES

Tarsus

Metatarsus

Digits

Flexor

surface

Flexor

surface

Flexor

surface

Flexor

surface

Sacroiliac joint

Hip joint

Stifle joint

Tarsal joints

Digital joints

of left pelvic limb.

the ischium meets the ilium. The coccygeus at-taches here. Caudal to this spine the border of the

ischium is depressed and marked by a series of low

ridges produced by the tendon of the internal ob-turator. This area is known as the lesser ischiatic

notch The gemelli arise from the

lateral surface adjacent to the lesser ischiatic notch.

The ramusof the ischium is the thin and wide

medial part of the ischium. It is bounded laterally

by the obturator foramen and blends caudally

with the body of the ischium. The ramus meets

its fellow at the symphysis and is fused with the

pubis cranially. The ischiatic tableis the flat por-tion where the ramus meets the body (Fig. 2-34). It

faces dorsally and is the site of origin of the inter-nal obturator muscle. The quadratus femoris and

the external obturator arise from its ventral sur-face. The ischiatic archis formed by the medial

portion of the caudal border of each ischium.

3. The pubis extends from

the ilium and ischium laterally to the symphysis

medially and consists of a body and two rami.

The bodyis located cranial to the obturator fora-men. The cranial ramusextends from the body to

the ilium and enters into the formation of the ace-tabulum. The caudal ramusfuses with the ischial

ramus at the middle of the pelvic symphysis. The

ventral surface of the pubis and adjacent ischial

ramus serve as origin for the gracilis, the adduc-tor, and the external obturator. The dorsal surface

gives rise to a small part of the internal obturator

and the levator ani. The obturator sulcus,a groove

for the obturator nerve, is located at the cranial

end of the obturator foramen and passes dorsally

over the pelvic surface of the body of the bone.

The iliopubic eminenceprojects from the cranial

border of the cranial ramus of the pubic bone. The

pectineus attaches to it. The pubic tubercleproj-ects cranially from the pubis on the midline. The

roughened cranial border of the pubis between

the iliopubic eminence and the pubic tubercle is

the pecten,to which the abdominal muscles at-tach by means of a prepubic tendon to be dissected

later. The prepubic tendon is composed primarily

of the tendons of the paired rectus abdominis and

pectineus muscles.

The acetabulum  is a cavity

that receives the head of the femur. Its articular

surface is semilunar and is composed of parts

of the ilium, ischium, and, in young animals,

the acetabular bone In the adult the

acetabular bone is fused imperceptibly with the

pubis, ischium, and ilium. The circumference of

the articular surface is broken at the caudomedial

part by the acetabular notch.The acetabular

fossais formed by the ischium and the acetabular

bone. The ligament of the head of the femur at-taches in this fossa. The fossa and the notch are the

nonarticular parts of the acetabulum. The two

sides of the notch are connected by the transverse

acetabular ligament.

The obturator foramenis closed in life by the

obturator membrane and the external and internal

obturator muscles that the membrane separates.

Read more »

Veterinary Dog Anatomy

Note: All the notes provided us from gcvs 

recomended book Guide To The Dissection Of Dog By Howard E. Evans, PhD 

Lecture no 4

BONES OF THE THORACIC LIMB(continued)

Veterinary Anatomy  GCVS 1st semester

Carpal Bones/Metacarpal Bones/Phalanges

Carpal Bones

The term carpus  is used to

designate that part of the extremity between the

antebrachium and metacarpus that includes all the

soft structures as well as the bones. The carpus in-cludes seven small, irregular bones arranged into

two rows. These are most conveniently studied

on radiographs. The proximal row contains three

bones. The largest of these, the intermedioradial

carpal(often referred to as the radial carpal), is on

the medial side and articulates proximally with

the radius. The ulnar carpalis the lateral member

of the proximal row. Its palmar portion projects

distally palmar and lateral to the fourth carpal

bone. The accessory carpal,the palmar member, is

a short rod of bone that articulates with the styloid

process of the ulna and the ulnar carpal bone andserves as a lever arm for some of the flexor muscles

of the carpus. The distal row consists of four bones

numbered from the medial to the lateral side. From

the smallest on the medial side, these are the first,

second, third, andfourth carpal bones.The fourth

carpal bone is the largest and articulates with the

base of the fourth and fifth metacarpals.

Metacarpal Bones

The metacarpus contains five

bones. The metacarpal bones are long bones in

miniature, possessing a slender body,or shaft,

and large extremities. The proximal extremity is

the base,and the distal one is the head.The meta-carpals, like the carpals and digits, are numbered

from medial to lateral. Proximally all articulate

principally with the corresponding carpal bones,

except the fifth, which articulates with the fourth

carpal. Distally all articulate with the correspond-ing proximal phalanges. Note the sagittal ridge on

the head for articulation with the sagittal groove

in the base of the corresponding proximal phalanx.

The interosseous muscles largely fill the intermeta-carpal spaces palmar to the metacarpal bones.

The first metacarpal bone is atypical. It is a ves-tigial structure, but unlike the first metatarsal bone

in the hindpaw, it is constantly present.

Phalanges

In the forepaw there are three phalanges for each

of the four main digits the first

digit, or pollex, a dewclaw, has two phalanges Each proximal and middle phalanx has a proximal

base,a body,and a distal head.

On the distal phalanx, a thin shelf of bone, the

ungual crest,overlaps the claw and forms a band

of bone around the proximal portion of the claw.

The ungual processis a curved conical extension

of the distal phalanx into the claw. The rounded

dorsal part of the base is the extensor processon

which the common digital extensor tendon is in-serted. A small process on the palmar surface is

the flexor tuberclefor insertion of the deep digital

flexor tendon.

Two proximal sesamoid bonesare located in

the interosseous tendons on the palmar surface of

each metacarpophalangeal joint (digits II–V). Four small dorsal sesamoid bones(none for the first

digit) are embedded in the common digital extensor tendons as they pass over the metacarpopha-langeal joints  

Read more »

Veterinary Dog Anatomy

Note: All the notes provided us from gcvs 

recomended book Guide To The Dissection Of Dog By Howard E. Evans, PhD 

Lecture no 3

BONES OF THE THORACIC LIMB(continued)

Veterinary Anatomy  GCVS 1st semester

Radius/Ulna

Radius

The radius and ulna are the bones of the antebra-chium, or forearm. It is important to know that

they cross each other obliquely so that the proxi-mal end of the ulna is medial and the distal end

is lateral to the radius. The radius (Fig. 2-6), the

shorter of the two bones of the forearm, articulates

proximally with the humerus and distally with the

carpus. It also articulates with the ulna, proximal-ly by its caudal surface and distally near its lateral

border.

The proximal extremity consists of head, neck,

and tuberosity. The headof the radius, like the

whole bone, is widest medial to lateral. It forms

proximally an oval, depressed articular surface,

the fovea capitis,which articulates with the

capitulum of the humerus. The smooth caudal

border of the head is the articular circumfer-encefor articulation with the radial notch of the

ulna. The small radial tuberositylies distal to

the neck on the medial border of the bone. The

biceps brachii and brachialis insert in part on

this tubercle.

Head

Capitular fovea

Articular

circumference

Radial tuberosity

Medial border

Trochlea

Styloid process

Articular face

Ulnar notch

Lateral border

Neck

Left radius, caudal view.

Guide to the Dissection of the Dog 12

The bodyof the radius is compressed so that it

possesses cranial and caudal surfaces and medial

and lateral borders. It is slightly convex cranially.

At the carpal end, the body blends without sharp

demarcation with the enlarged distal extremity.

The caudal surface of the radius is roughened and

slightly concave. It has a ligamentous attachment

to the ulna. Distally it broadens and becomes the

expanded caudal surface of the distal extremity.

The cranial surface of the radius, convex trans-versely, is relatively smooth throughout.

The distal extremity of the radius is the troch-lea.Its carpal articular surface is concave. On the

lateral surface of the distal extremity is the ulnar

notch,a slightly concave area with a facet for ar-ticulation with the ulna. The medial surface of the

distal extremity ends in a rounded projection, the

styloid process.The medial collateral ligament of

the carpus attaches proximal to the styloid process.

The cranial surface of the distal extremity presents

three distinct grooves. The most medial groove,

which is small, short, and oblique, contains the

tendon of the abductor digiti I longus. The middle

and longest groove, extending proximally on the

shaft of the radius, is for the extensor carpi radi-alis. The most lateral of the grooves on this surface

is wide and of variable distinctness. It contains the

tendon of the common digital extensor.

Ulna

The ulna is located in the caudal part of

the forearm. It exceeds the radius in length and

is irregular in shape and generally tapers from

its proximal to its distal end. Proximally the ulna

is medial to the radius and articulates with the

trochlea of the humerus by the trochlear notch

and with the articular circumference of the radius

by the radial notch.This forms the elbow. Distally

the ulna is lateral and articulates with the radius

medially and with the ulnar and accessory carpal

bones distally.

The proximal extremity is the olecranon,which

includes the olecranon tuber and the anconeal

process. It serves as a lever arm for the extensor

muscles of the elbow. It is four sided, laterally

compressed, and medially inclined. Its proximal

end, the olecranon tuber,is grooved cranially and

enlarged and rounded caudally. The triceps bra-chii, anconeus, and tensor fasciae antebrachii at-tach to the caudal part of the olecranon. The ulnar

portions of the flexor carpi ulnaris and deep digi-tal flexor arise from its medial surface.

The trochlear notchis a smooth, vertical, half-moon–shaped concavity facing cranially. The

whole trochlear notch articulates with the trochlea

of the humerus. At its proximal end a sharp-edged,

slightly hooked anconeal processfits into the olec-ranon fossa of the humerus when the elbow joint

is extended. At the distal end of the notch are the

medialand lateral coronoid processes,which ar-ticulate with the humerus and radius. The medial

coronoid process is larger. Between these processes

is the radial notch for articulation with the articu-lar circumference of the radius.

The bodyof the ulna is three sided in its middle

third; proximal to this the bone is compressed lat-erally, whereas the distal third gradually loses its

borders, becomes irregular, and is continued by

the pointed distal extremity. The ulnar tuberosity

is a small, elongated eminence on the medial sur-face of the bone at its proximal end, just distal tothe medial coronoid process. The biceps brachiiand the brachialis insert on this eminence. The in-terosseous borderis distinct, rough, and irregu-lar, especially at the junction of the proximal and

middle thirds of the bone, where a large, expan-sive, but low eminence is found. This eminence

indicates the place of articulation with the ra-dius by means of a heavy ligament. Frequently,

a vascular groove medial to the crest marks the

position of the caudal interosseous artery. This

groove is most conspicuous in the middle third

of the ulna. The body shows a distinct caudal

concavity.

The distal extremity of the ulna is the head with

its prominent styloid process.A part of this pro-cess articulates with the ulnar and accessory car-pal bones. The head articulates medially with the

radius.

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Veterinary Anatomy

Note: All the notes provided us from gcvs 

recomended book Guide To The Dissection Of Dog By Howard E. Evans, PhD 

Lecture no 2

BONES OF THE THORACIC LIMB(continued)

Veterinary Anatomy  GCVS 1st semester

Humerus

The humerus is located in the arm, or

brachium. This bone enters into the formation of

both the shoulder joint and the elbow joint. The

shoulder joint is formed by the articulation of the

scapula and humerus; the elbow joint is formed

by the articulation of the radius and ulna with

each other and with the humerus. The proximal

extremity of the humerus includes the head, neck,

and the greater and lesser tubercles. The distal ex-tremity, the condyle, includes the trochlea, capitu-lum, and the radial and olecranon fossae, which

communicate proximal to the trochlea through the

supratrochlear foramen. The medial and lateral

epicondyles are situated on the sides of the con-dyle. The body of the humerus lies between the

two extremities.

The headof the humerus is the part that articu-ates with the scapula. It presents more than twice

the area of the glenoid cavity of the scapula and

is elongated sagittally. Although the shoulder joint

is a typical ball-and-socket joint, it normally under-goes only flexion and extension. The intertubercu-lar groovebegins at the cranial end of the articular

area. It lodges the tendon of origin of the biceps

brachii and is deflected toward the median plane by

the greater tubercle,which forms the craniolateral

part of the proximal extremity. The greater tubercle

is convex at its summit and, in most breeds, higher

than the head. It is continued distally in the body

of the humerus by the crest of the greater tubercle.

The greater tubercle receives the insertions of the

supraspinatus and the infraspinatus and part of the

deep pectoral. Between the head of the humerus

and the greater tubercle are several foramina

for the transmission of vessels. The infraspinatus is

inserted on the smooth facet on the lateral side of

the greater tubercle. The lesser tuberclelies on the

medial side of the proximal extremity of the hu-merus, caudal to the intertubercular groove. It is

not as high or as large as the greater tubercle. The

subscapularis attaches to its proximal border. The

neckof the humerus is not distinct except caudally.

It is the line along which the head and parts of the

tubercles have fused with the body.

The cranial surfaceof the humerus is distinct

in the middle third of the body, where it furnishes

attachment for the brachiocephalicus and part of

the pectorals. Distally it fades but may be consid-ered to continue to the medial lip of the trochlea.

On the proximal third of the cranial border are

two ridges. They continue to the cranial and cau-dal parts of the greater tubercle. The ridge that ex-tends proximally in a craniomedial direction is the

crest of the greater tubercleand is also the cranial

border of the bone. This forms part of the area of

insertion of the pectorals and the cleidobrachialis.

The ridge extending to the caudal part of the

greater tubercle is on the lateral surfaceof the hu-merus. Distally it is thickened to form the deltoid

tuberosity.The deltoideus inserts here. From this

tuberosity to the caudal part of the greater tubercle,

the ridge forms the prominent tricipital line. The

lateral head of the triceps arises from this line. The

teres minor inserts on the tuberosity of the teres

minoradjacent to the proximal extremity of the tri-cipital line. The smooth brachialis grooveis on the

lateral surface of the body. The brachialis, which

originates in the proximal part of the groove, spirals

around the bone in the groove so that distally it lies

on the craniolateral surface. Distal to this groove is

the thick lateral supracondylar crest.The extensor

carpi radialis and part of the anconeus attach here.

The crest extends distally to the lateral epicondyle.

The caudal surfaceis smooth and rounded trans-versely and ends in the deep olecranon fossa.

The crest of the lesser tuberclecrosses the prox-imal end of the medial surfaceand ends distally at

the teres major tuberosity.The teres major and la-tissimus dorsi are inserted on this tuberosity. Cau-dal and proximal to this, the medial head of the

triceps arises and the coracobrachialis is inserted.

Approximately the middle third of the medial sur-face is free of muscular attachment and is smooth.

The distal end of the humerus, including its ar-ticular areas and the adjacent fossae, is the humeral

condyle.The articular surface is divided unevenly

by a low ridge. The large area medial to the ridge

is the trochlea,which articulates with both the ra-dius and the ulna and extends proximally into the

adjacent fossae. The articulation with the trochlear

notch of the ulna is one of the most stable hinge

joints (ginglymus) in the body. The small articular

area lateral to the ridge is the capitulum,which

articulates only with the head of the radius.

The lateral epicondyleis smaller than the me-dial one and occupies the enlarged distolateral

end of the humerus proximal to the capitulum. It

gives origin to the common digital extensor, lateral

digital extensor, ulnaris lateralis, and supinator.

The lateral collateral ligament of the elbow also

attaches here. The lateral supracondylar crest ex-tends proximally from this epicondyle and is the

origin for the extensor carpi radialis.

The medial epicondyleis the enlarged disto-medial end of the humerus proximal to the trochlea.

Its caudal projection deepens the olecranon fossa.

The anconeus arises from this projection. The ele-vated portion of the medial epicondyle serves as

origin for flexor carpi radialis, flexor carpi ulnaris,

pronator teres, and the superficial and deep digital

flexor muscles. The medial collateral ligament of

the elbow also attaches here.

The olecranon fossais a deep excavation of the

caudal part of the humeral condyle. It receives the

anconeal process of the ulna during extension of

the elbow. On the cranial surface of the humeral

condyle is the radial fossa,which communicates

with the olecranon fossa by an opening, the supra-trochlear foramen.No soft structures pass through

this foramen.

Radius

The radius and ulna are the bones of the antebra-chium, or forearm. It is important to know that

they cross each other obliquely so that the proxi-mal end of the ulna is medial and the distal end

is lateral to the radius. The radius (Fig. 2-6), the

shorter of the two bones of the forearm, articulates

proximally with the humerus and distally with the

carpus. It also articulates with the ulna, proximal-ly by its caudal surface and distally near its lateral

border.

The proximal extremity consists of head, neck,

and tuberosity. The headof the radius, like the

whole bone, is widest medial to lateral. It forms

proximally an oval, depressed articular surface,

the fovea capitis,which articulates with the

capitulum of the humerus. The smooth caudal

border of the head is the articular circumfer-encefor articulation with the radial notch of the

ulna. The small radial tuberositylies distal to

the neck on the medial border of the bone. The

biceps brachii and brachialis insert in part on

this tubercle.

Head

Capitular fovea

Articular

circumference

Radial tuberosity

Medial border

Trochlea

Styloid process

Articular face

Ulnar notch

Lateral border

Neck

Left radius, caudal view.

Guide to the Dissection of the Dog 12

The bodyof the radius is compressed so that it

possesses cranial and caudal surfaces and medial

and lateral borders. It is slightly convex cranially.

At the carpal end, the body blends without sharp

demarcation with the enlarged distal extremity.

The caudal surface of the radius is roughened and

slightly concave. It has a ligamentous attachment

to the ulna. Distally it broadens and becomes the

expanded caudal surface of the distal extremity.

The cranial surface of the radius, convex trans-versely, is relatively smooth throughout.

The distal extremity of the radius is the troch-lea.Its carpal articular surface is concave. On the

lateral surface of the distal extremity is the ulnar

notch,a slightly concave area with a facet for ar-ticulation with the ulna. The medial surface of the

distal extremity ends in a rounded projection, the

styloid process.The medial collateral ligament of

the carpus attaches proximal to the styloid process.

The cranial surface of the distal extremity presents

three distinct grooves. The most medial groove,

which is small, short, and oblique, contains the

tendon of the abductor digiti I longus. The middle

and longest groove, extending proximally on the

shaft of the radius, is for the extensor carpi radi-alis. The most lateral of the grooves on this surface

is wide and of variable distinctness. It contains the

tendon of the common digital extensor.

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