Osteology (frog, rabbit, fawl, varanus), Study notes of Zoology

Download Osteology (frog, rabbit, fawl, varanus) and more Study notes Zoology in PDF only on Docsity! The living Amphibia do not possess an exoskeleton. The endoskeleton of frog is made partly of cartilage and partly of bone. In the early stages of development (tadpole), the skeleton is solely cartilaginous but, in the adult frog, it is greatly replaced by bones called the cartilage or replacing bones. Bones become also developed in other parts of skin or dermis of certains regions where there was no pre- existing cartilage. Such bones are termed membrane bones, A part of primary cartilaginous skeleton is impregnated by calcium salts and becomes hard. This is known as the calcified cartilage, As usual, the skeleton is conveniently divided into axial and appendicular skeleton, Axial skeleton includes skull, vertebral column and sternum which lie along the median longitudinal axis of body. Appendicular skeleton comprises the skeleton of the limbs and the girdles supporting them (Fig. 1). CHARA STIC FEATURES SKULL ee Skull of frog is characterized by the following important characters : (1) It is triangular in shape, broad and dorso-ventrally flattened. (2) A considerable part of chondrocranium of tadpole persists in the adult. A large part of cranium and sense capsules consists of cartilage. . (3) Cranium is comparatively small and narrow due to small size of brain which it encloses. ~ Frog jerort of gone gi facet for 9th vertebra itium iliac crest articular surface for urostyle ischium ischium acetabulum iliac crest — | Pelvic girdle. A. Dorsal view. B. One minatum) in lateral view. head || deltoid — ridge I articular facet for =a Fig, 1. Frog. Forelimb wns olecranon process \ cavity for trochlea of humerus radius ulna } “ree | shat | groove metacarpals of ulna \ distal ( \ oe K capitulum \ epiphysis “) capitohamatum | T Ys 7 \ articular surface VY condyle—_*« for carpals phalanges (Posterior view) (Anterior view) HUMERUS RADIO-ULNA BONES OF HAND 627 with the bone of the other half at a median ischiatic symphysis, It is slightly bigger than pubis and oval in shape. FORELIMB BONES !, Humerus. Bone of the upper arm is called humerus. It is a short and cylindrical bone with a slightly curved shaft, Its proximal end is swollen to form a rounded hiead, which fits into the glenoid cavity of pectoral girdle. Head is covered by calcified cartilage. Below the head, the proximal half of shaft bears anteroventrally a Prominent vertical process, the deltoid ridge, to which muscles are attached. Distal end shows a round prominence, the capitulum or trochlea, with a condylar ridge on either side. It articulates with the groove of radio-ulna (Fig. 11). 2. Radio-ulna. Forearm contains a compound bone, called radio-ulna, formed by the fusion of radius and ulna bones. Proximally, the radio-ulna shows a concavity to receive the trochlea of humerus and further projected into an olecranon process forming the elbow joint Distal half of radio-ulna is somewhat flat and a groove distal epiphysis radio-ulna ‘4 intermedium ulnare radiale  Endoskeleton of Varanus of cartilage and partly cartilage or replacing bones, and Endoskeleton of Varanus may be and appendicular portions. Axial skeleton forms the median longitudinal axis of body and includes skull, vertebral column, ribs and sternum. Appendicular skeleton includes limb-bones and girdles supporting them (Fig. 1). jeton of Varanus is made partly of bone. Bones are of two types membrane or investing bones. conveniently divided into axial The endoskel CHARACTERIST Skull of Varanus is characterized by the following important features : (I) It is more or less elongated and flaticned with narrow anterior end, and includes @ 2) It is quite complicated in structure and form, large number of replacing and inv! 8) I 's monocondylic, as a single con W) anaes with atlas vertebra. a / ane we because a thin median, vertical interorbital septum Chnium ie © two orbits. Alpen ae but stron orbitosphenoids and presphenoid b Two mite ot and postorbital bones a median varietal om fused into a single bone, perforated by a nee into a single bone. Anteriorly, two premaxillac become emporal regi . temporal aie of skull on either side shows three vacu ssae-posterior, lateral and superior. esting boncs. dyle formed by basioccipital ones are absent, es are present. 8 a tities OF » yfoskeleton of Varanus : epipubis pubis ligament foramen for bis prep obturator nerve igchio-pubie fenest’a Preacetabular v process of ilium | acetabulum ischium hypoischium U ilium preacetabular process of ium ischium foramen for obturator nerve acetabulum ilium’ at . ischiatic symphysis pubis prepubis | A B \ emit ca mee ETS oe straw ro . Fig. 9. Varanus. Pelvic girdle. A. Complete in ventral view. B. Left half in ventral view. obs ; which it is performed by a small foramen which y PELVIC GIRDLE transmits the obturator by nerve. Just external to | The pelvic girdle also consists of two similar | halves or ossa innominata, Each os innominatum \ jg a triradiate structure, each ray represented by a \ distinct bone. The three bones (ilium, pubis and ' ischium) are very hard and solid and joined with each other but not fused together. On the outer _ surface, at the point where the three bones meet, is a concave articular surface, the into which fits the head of femur. In the depression of acetabulum, the lines of union of the bones are clearly visible (Fig. 9). i. lium. Iium is a strong, compressed, rod-like bone, directed backwards and upwards to ' articulate with sacral vertebra. Ilium contributes (0 nearly one-third of acetabulum, in front of a gives off from its outer side a small, Tob-like preacetabular process. carved es Pubis is a flattened, somewhat from the ne, passing downwards and forwards Piao to meet its fellow of the Ventral tine a pubic symphysis along the mid- pipubis ie A small nodule of cartilage, the the aero en in front of symphysis between “Ontrbutes to ab s of two pubis. Pubis also Out one-third of acetabulum, near ‘ and slightly posterior to this foramen, pubis is produced into a small rod-like process, called is, which is directed outward. schium. It is a flat, somewhat oblong and curved bone, running medially from acetabulum to meet its fellow of other side at an isciiiati symphysis, A small rhomboidal or rod-like piece of calcified cartilage, called hypoischium, or os wea, passes backwards from ischiatic symphysis and supports the ventral wall of cloaca. A wide space is enclosed between pubes and ischia, which is divided by a median ligament inte two lateral ischio-pubic iestrae, The median ligament extends between the two symphyses and is often lost in a dried girdle. FORELIMB BONES : Upper arm contains a single bone called humerus. It is made of an elongated shaft with greatly expanded extremities covered by epiphyses of calcified cartilage. Proximal end bears a rounded eid, which fits into the glenoid cavity of pectoral girdle. A biciita! is enclosed foss  between head and a medial process of proximal end. Below head is present a prominent crest-like ‘toid ridge. Distal end of humerus bears a pulley-like structure, the trochlea, made of two articular surfaces, or epicondyles, one for radius and other for ulna (Fig. 16). 2. Radius and Ulna. Forearm contains two bones, radius and ulna, Radius is slender and composed of a shaft and two epiphyses. Distal end of radius bears a concave articular facet for carpus, and a preaxial styloid process. Uina is stouter than radius. Proximally it is produced into an upwardly directed olecranon | while distally it bears a convex articular surface for carpus. 3. Bones of forefoot. Wrist or carpus contains 10 small bony pieces or carpals. These are rounded, polyhedral in shape and arranged in two rows. Proximal row contains 3 carpals : radiale, ulnare and intermedium. Distal row has 5 carpals. A centrale lies in between the two rows, while a pisciform is attached to the distal epiphysis of ulna on its postaxial side. The manus is supported by five elongated metacarpals and bears five digits composed of olecranon process radius bicipital fossa head a ulna centrale ulnare deltoid ridge intermedium shaft adiale epicondyle HUMERUS RADIUS-ULNA 3 BONES OF HAND | Fig. 10. Varanus. Forelimb bones. | _ Endoskele. 2, 3,4, 5 and 3 phalanges, respectively, Term phalanx bears a horny claw. inal HIND LIMB BONES —_—_—___-_"""r——————V 1. Vemur. Thigh contains a single stout bon the femur. It has an elongate shaft ang tue epiphyses. Proximal end bears a rounded hea which fits into acetabulum. Besides, it shows , prominence on preaxial side, called lesser trochanter, and a minor prominence on POstaxia} side, called greater trochanter, Distal end of femur is pulley-shaped, composed of two condyles and a tuberosity, for articulation with tibia ang fibula (Fig. 11). pin and fibula. Shank or crus contains two bones, tibia and fibula. ‘Tibia is on preaxial side. It is a stout and somewhat curved bone. Its proximal end bears two concave facets for distal condyles of femur. Proximal end also carries, on its anterior or dorsal surface, a longitudinal ridge, crest. }ibula is comparatively called emial head greater tuberosity tibiale +intermedium fibulare +centrale shaft 4+5 3 tarsals tarsal 142 tarsals Vv TIBIA-FIBULA & BONES OF FOOT FEMUR Fig. Ul. Varanus. Hind limb — ; Fowl cofeion Of phe pode “ postacetabular iliurn ilioischiatic =\ ( — formen ~A \ ~ ischium— 12. Fowl. Pelvic girdl PELVIC GIRDLE _ thy features of pelvic girdle are as wOrly Note’ tl gence of a ventral symphysis. This is in i aocordance with the laying or relatively large cee and extensive fusion of pelvic girdle 8 ih synsacrum of vertebral column. It snmpensates for the weakness which would otherwise result from the absence of a symphysis, and serves for bipedal locomotion. 3) Incomplete ossification of acetabulum, which is partially membranous at its bottom. Pelvic girdle is large and consists of two separate halves. Each half is known as 0s imominatum or innominate which is composed of the usual three elements : ‘ium, iveiium and pubis, Junction of the three is marked by a deep socket on outer side, the » m, which receives the rounded head of femur, forming atypical ball and socket joint (Fig. 12). |. tllum. It is an elongated lamellar bone ‘hich may conveniently be divided into sie ier ban Hostal parts of equal teasers py fro ilium is firmly united with Sinsacrum, ones and neural spines _ of 'S concave stile aumace of preacetabular ilium Ox, Diam forms at of postacetabular ilium is On the poster " the dorsal part of acetabulum, order of which it projects Preac antitrochanter surface © ay Preacetabular ium Right os innominatum in outer view, ] into a small Process, the anti-irochanter, for articulation with the great trochanter of femur. Under surface of ilium shows two depressions for the kidney lobes. 2. Ischium. It is a broad, lamellar almost vertical bone extending behind the acetabulum, of which it forms about a third. It is fused posteriorly with ilium but separated anteriorly from it by a large oval ilio-ischiatic foramen. 3. Pubis. Pubis is a thin, slender and curved strip of bone running along the ventral edge of ischium. It forms a small ventral part of acetabulum, in front of which it projects forwards as a small blunt preacctabular or pre-pubic process. Behind the acetabulum, pubis is separated from ischium by a small, oval obturator foramen, behind which the two bones are joined for a short distance only. Free posterior end of pubis extends backwards for some distance beyond the ischium. BONES OF A FORELIMB OR WING Wing of bird corresponds to the forelimb of a mammal, but it differs from it in many respects. (1) In adaptation to flight, wing of a bird has much less flexibility of parts than in the forelimb of a mammal. (2) Radius and ulna do not move upon each other. 600 an | pneumatic foramen cups for ayaa head distal | | conse ] al humerus deltoid | tidge | ; i olecranon radius | fossa | coronoid i fossa curved | axial | condyles { surface of ulna sigmoid ‘ notch } \ Endoskele On ay fused distal ¢, arpal bones "Pal K olecranon / process Si melacarpay nutrient ( i) foramen \ uina 1 " | | metacarpal | | radiale Mm | carpal metacarpal | intercondylar groove | HUMERUS RADIUS & ULNA CARPOMETACARPY (Anterior view) (Posterior view) 5 —_—$$—$——__ Fig. 13. Fowl. Forelimb bones. (3) Distal carpals fuse with metacarpals to form carpometacarpus. (4) Only three digits are present. nerus. Upper arm bone or I ily curved and expanded | end presents a smooth convex surface or head which articulates with glenoid cavity, formed by scapula and coracoid bones. It is bordered by two tuberosities or (ubercles, Preaxial or smaller tuberosity shows a prominent crest or deltoid ridge for insertion of great pectoral and deltoid muscles. Postaxial or greater tuberosity carries a large pneumatic foramen, communicating with an air cavity in the shaft of bone. Distal end of humerus bears a pair of convex trochlear articular surfaces or condyles for radius and ulna. 2. Radius and ulna. Forearm has two separate bones, radius and ulna. Radius is shorter, slender, straight and preaxial. Its proximal end forms a shallow cup bo areal wih ie outer or preaxial condyle : ¢ is. Its distal end bears a knob which fits into the radiale carpal. Una is longer, stouter, postaxial and more curved than radius, so that a wide space is enclose q enclosed between wre ive bones. Its proximal end or the inner or postaxial 1. Wor humerus is stout, elongated, slig! at both ends. Proximal condyle of trochlea of humerus and js fun projected into a small, blunt olecranon e Its distal end articulates with the ulnare cup al and radius. 3. ¢ als. Wrist or carpus of adult Contains only two irregular bones. Of these, the smatey and preaxial 120 articulates with radius whil the larger and postaxial wloare articulates wit ulna. These represent the proximal row of carpals as in rabbit. The embryo also contains a distal row of carpals but they fuse with the metacarpal in adult. 4. Ca Manus or palm in adult contains a single elongated bone, the ea’) xX It is a compound bone formed by the fusion of three saypals with distal ow of carpals. | arpal is the shores, represented by a small stumpy projection at the proximal end of composite bone on preaxial side se I is by far the strongest and stacarpal is slightly curvel fe sevotl me straight bone. outwardly and is more slender than th with which it is fused at both ends. Ic is pe on the postaxial side. 5. Phalanges. There are three clawles or lingers, borne by the three metacarpal contain small rod-like bones called!" , Preaxial or , consists of a gil. 661 has two phalanges has only a single HIND LIMB BONES of bird, modified for bipedal resemble those of rabbit in position ental plan. However, they are the absence of a tarsus, so int becomes inter-tarsal or jimbs tion, damn pid joco? and yerized DY chara le jo! ie nt yr, Thigh contains a single cylindrical, han and slightly curved bone with alled femur. Its proximal end de a rounded head which fits d, on outer side, a prominent . Between id trochanter is an articulating surface anti-rochanter_ of ilium. Distal end of pulley-like structure consisting of esd St stout ort but hort attened ends, 6 1 inner si ead an for the an femur carries @ bounded laterally by two prominent cond) for articulation with the tibiotarsus. Outer condyle 1» deeply grooved to receive the upper end of fibula. A sesamoid bone, the patella, is found in the tendon in front of the femur-tibiotarsal joint. Sesamoid bones are ossified parts of tendons. 2. Tibio-tarsus and fibula, Shank contains two bones, a tibio-tarsus and a fibula. Tibio-tarsus is a stout, nearly straight bone, even longer than femur. It is formed by the fusion of fibia with proximal row of tarsals (astragalus and calcaneum). It lies on the preaxial or inner side of shank. Its broad proximal end bears two articular facets for the two condyles of femur, and gives out in front a prominent cnemial crest. The distal pulley-like end shows a smooth groove bounded by two articular condyles for the tarso- metatarsus. Fibula is reduced to a small, slender bone, closely applied to the outer or postaxial surface of tibio-tarsus. Its broad proximal end or head articulates with the outer condyle of femur. Its distal end does not reach the ankle but tapers to ; interco! f ove a shi joint. an anterior deep intercondylar fossa or ap Pi Pe REE ST AS IE ———— great trochanter head of tibial crest articular facets for tibiotarsus ma / head“ ! fibula nutrient | ) foramen |\ \\ distal condyles i} ' tibiotarsus distal nodule of |} \ groove | metatarsal [yj ! distal / inter fy lateral | ( condylar tubercle \, \ " metatarsal a) i i iN metatarsal | outer condyle - condyles NV metatarsal (Anterior FEMUR TIBIOTARSUS TARSOMETATARSUS TARSOMETATARSUS view) (Posterior view) FIBULA OF FEMALE OF MALE henna {Anterior view) (Posterior view) (Anterior view) TE MOR oR MTS Fig. 14. Fowl. Hind Sere limb bones. | articular » sacrum cotyloid / bone obturator foramen ischium pubic symphysis A surface for acetabulum ischial tuberosity ischial tuberosity obturator —\_f) B foramen Fig. 10, Rabbit. Pelvic girdle, A. Complete girdle in ventral view. B. Left tt but a small cotyloid bone prevents pubis from reaching up to acetabulum. Ilium is the large antero-dorsal and blade-like bone, joined to sacrum at about the middle of its length by a prominent crescentic articular surface. Towards acetabulum it becomes narrower, Ischium forms the postero-dorsal part of innominate bone. Its posteriormost thickened portion, called ischial tuberosity, is produced outwards and forwards into a hook-like process. Pubis is a small, slender bone forming the ventro- median portion of innominate bone. It is separated from ischium by a large oval space, the oblurator foramen, Pubes of two sides unite mid-ventrally at a pubic symphysis, FORELIMB BONES Humerus. It is a relatively short but stout rod- like bone of upper arm. Proximally, it bears a large rounded head articulating with glenoid cavity of scapula. Close to head are a greater tuberosity on outer, and a lesser tuberosity on inner side. Between these two tuberosities is a bi groove. In upper or proximal a slight deltoid ridge on the break bear side. It serves for attachment of muscles, fy leroy humerus bears a pulley-like troche sth, articulation with ulna. Just above trochl or present two depressions or supra ate communicating with each other through as trochlear foramen, Anterior or coracoiq fo smaller while posterior or olecranon fos larger into which fits the olecranon proces is ulna (Fig. 11). Sof si 2 ou Forearm contains two separate bones, radius and ulna, put they ar tightly bound together at the two ends, Raid ys ; small and somewhat curved so that proximally , lies in front of ulna, but distally on its inner site es is continued proximally into a promize olecranor to articulate with olecran» ‘ossa_ of humerus. Basally this process is notched by the sigmoid notch into which fits the troche of humerus. Distally the two bones bear epiphyss and articulate with carpals. »refoot or hand. Wrist or carpus contains 9 small rows. These are in proximal row, one Bones of | bones arranged in te ye Rabbit “tt! 677 i: Neen, a iesse! meal bicipital fossa Z opiphysas pe 2 G - YS. - olecranon rachus es je ‘ f greater roces! adil 4 tuberosity process radiale Anat i sigmoid Wapezium 1 intermectism | notch trapezoid uneitoren i f | nF radius + i i centrale pomatacarya's | phalanges | | \ supre-trochlear \ olecranon My “ae 1 ond | Jeane fossa —ulna | 1oss4 \ | , | \, 2 ° | trochlea ‘——epiphyses 7 {| 3)4 claws yMERUS HUMERUS BONES OF HAND inate view) (Posterior view) (Side view) RADIUS-ULNA magnum and uneiform in distal row. rej resents the fusion of two carpals. In sesamoid bone, pisciform, is present yentral side of carpus. There are five the 9 i of ved net arpals supporting the manus and along : 3, 3, phalanges, «digits with 2, 25 > ie het The terminal phalanx bears a horny regentively- cla HIND-LIMB BONES ee von Itig the bone of thigh region. It is the ‘gest and the stoutest bone of body. It has a ing cylindrical shaft with expanded extremities. Protimal end bears on the inner side a prominent rounded head for articulation with acetabulum of relic girdle. It also bears a rough eminence, the , chanter above the head, a below the head, and a — we the greater trochanter. The ve for muscle attachment. The dee} mee bordered by : Wale , y head and greater trochanter ‘ossa, Distally, the femur bears a ture made of two lateral co 1 roove, for articulation Ply str “eng a in Fig. 11. Rabbit. Forelimb bones. with tibio-fibula. Anteriorly this groove is termed the patellar groove, because in it slides a tendon containing the sesamoid bone, patella or knee cap. Tibio-fibula. Shank contains two bones— a large, stout and straight tibia, and a small, slender fibula. The two bones are free proximally but fused distally, hence the name {ibio-fibula. Its proximal end bears anteriorly a small but sharp ridge, the cnemial crest and articulates by two depressions with the two femoral condyles. Fibula lies on the postaxial side. Bones of | yt. Ankle or tarsus contains 6 farsal bones arranged in two rows. {ibiale and um of proximal row are fused to form us lying on the preaxial side. Other bone of proximal row, called calcancum, is the largest tarsal bone, produced into a spur or process behind its articulation with tibio-fibula. It occupies the post-axial side. A single centrale lies just in front of astragalus. Distal row includes three and ectocuneiforr bones socuneiform, There are 4 long slender, varsal bones supporting the sole or pes, the firs First toe or fia llus is also absent so that the only four toes, each composed of three pli! the terminal one of which bears a claw. being absent.  oo Endosketetoy, ‘ fibulare or head ib calcar al ey} proximal neum stag, J epiphysis Me } o 4 4+5 etry wissen VY] poner distal ] / 3rd crest tarsals nq lesser trochanter dis, trochanter t al , atsal i fibula i ‘Mey i 3r tata inter / patellar distal » condylar shaft groove fia tarsal | groove Phalange, 1% i 5 distal wo SN articular . A surface j for claws condyles condyles tarsals | 4'3 RIGHT FEMUR — RIGHT FEMUR LEFT TIBIO-FIBULA | (Back view) (Front view) (Front view) BONES OF Hinp Foor ae cman ns | Fie 12. Rabbit, Hind limb bones. | Important . ~~) Questions >> type questions 1. Give an account of the skull of rabbit, 2. What is the basic structure of a vertebra ? Describe various types of vertebrae found in rabbit. yy Short answer type questions 1. Write short notes on the following bones of rabbit : (i) Atlas vertebra, (ii) Lower jaw, (iti) Pectoral girdle, (vB girdle, (v) Periotic bone. >>! iswer type question 1, What are the number of phalanges in the manus of rabbit ? 2. Which bone bears cnemial crest, what is its function ? 3. How many floating ribs occur in rabbit ? 4. What is os-innominatum, how many bones form it ? >> 8 1. The skull of rabbit has short-cranial part and long facial part. 2. The three otic bones of skull of rabbit are well-developed free bones. 3. Through stylomastoid foramen passes VII cranial nerve. 4, Cribriform plate is formed by frontal bones. S. The flask shaped bone tympanic bulla is formed by tympanic and periotic. >> Sacrum is formed by fusion of .. sacral vertebra. Metacromian process and acromian process are Present in... eee