LBYZOOL Activity 07-09 (Lab Exam 3)

Toad External Anatomy, The Skeletal System, & The Muscular System

Anura

Order frogs and toads belong in

Frog

- "Rana pipiens"
- smooth or slimy skin that is moist
- long, strong, hind legs that aid them in leaping
- big bulging eyes

Toad

- "Rhinella marina"
- thicker, bumpy, skin that is usually dry
- shorter hind legs, more suitable for walking
- more subtle eyes

2 Major Layers of Frog Skin

Epidermis & Dermis

Epidermis

layer of frog skin:

- stratified epithelium
- has 2 sublayers: stratum corneum & germinativum

stratum corneum

sublayer of frog epidermis:

- outermost stratified layer
- thin dead squamous keratinized cells
- constantly removed when shed

Ecdysis

- aka molting
- process when frogs shed its skin

stratum germinativum

sublayer of frog epidermis:

- living cuboidal to columnar stratified epithelial tissue
- continuously divide to replace the shed-off layer

chromatophores

- connective tissue which contains pigments
- at the junction of epidermis and dermis

melanophores

black pigment containing cells found at the junction of the dermis and epidermis

Dermis

layer of frog skin:

- inner layer of skin
- has 2 sublayers: stratum laxum/spongiosum & compactum

stratum laxum/spongiosum

layer of frog dermis:

- outer sublayer of dermis
- loosely arranged connective tissue & blood vessels
- cutaneous glands gives spongy appearance

cutaneous glands

posion glands & mucous glands

poison gland

gland in stratum laxum/spongiosum:

- larger glands
- less numerous
- posses thin epithelial wall
- blue arrow

mucous glands

gland in stratum laxum/spongiosum:

- small
- more numerous
- thicker wall
- red arrow

stratum compactum

layer of frog dermis:

layers of white fibrous connective tissue

dorsal

back or upper surface of an organism

ventral

stomach or lower surface of an organism

anterior

head end of an organism

posterior

tail end of an organism

bilateral symmetry

left & right halves of an organism are mirrored portions

main axis of toads

horizontal axis

3 planes of the toad body

frontal, sagittal (longitudinal), & transverse (cross)

frontal

plane dividing the body into dorsal & ventral sections

sagittal

plane dividing the body into left & right sections

transverse

plane dividing the body into anterior & posterior sections

locations relative to the center of the body

medial, lateral, proximal, proximal, & distal

medial

location near the middle

lateral

location to the sides

proximal

part of a structure that is nearer the origin

distal

part farther from the origin

regions of the body

axial & appendicular regions

axial region

region:

- head & trunk
- joined together by a very short neck, thereby restricting movement of the head
- structural functions

head

portion in axial region:

contains snout, mouth, external nares, eyes, browspot, tympanic membrane, & paratoid gland

snout

external part of head:

- blunt apex found on the tip of the head
- most anterior portion of the head

mouth

external part of head:

- for feeding
- extending tongue

external nares

external part of head:

- paired openings at the tip of the snout connected to internal nares (breathing)
- arrow 1

eyes

external part of head:

- dorsolateral portion of the head
- used to push down food; closes when they swallow
- contains: upper & lower eyelids, nictitating membrane

upper eyelid

part of eye:

thicker eyelid; does NOT move

lower eyelid

part of eye:

thinner eyelid; moves

nictitating membrane

part of eye:

- thin, transparent
- protects eyeballs
- keeps eyes moist when underwater
- arrow 2

browspot

external part of head:

- circular spot between the eyes
- displays where part of the skull development took place

tympanic membrane

external part of head:

- Posterolateral to the eye
- ovoid region of tightly drawn skin
- frog’s ear / ear drum
- covers auditory canal
- protects inner ear from outer environment
- arrow 3

paratoid gland

external part of head:

- behind tympanic membrane at each side of head
- large swelling
- large aggregate of poison glands
- secrete poisonous mucus
- only found in toad
- arrow 4

Croak

- only male frogs can do this
- to find a mate & defend their territory

Trunk

portion in axial region:

contains sacral hump & cloacal aperture

sacral hump

external part of trunk:

pelvis is elongated and higher at the spine

cloacal aperture

external part of trunk:

- aka anus
- most posterior part of the trunk on the dorsal side
- exit cavity for excretory, urinary, reproductive system

appendicular region

region:

- forelimbs & hindlimbs
- function for movement

Forelimbs

portion in appendicular region:

- anterior pair
- short
- used to raise or support the body when the frog is at rest
- contains: upper & lower arm, wrist, & hand

brachium

external part of forelimbs:

- upper arm
- arrow 6

antebrachium

external part of forelimbs:

- lower arm / forearm
- arrow 5

carpus

external part of forelimbs:

wrist

manus

external part of forelimbs:

- hand
- 4 digits + prepollux

prepollux

5th rudimentary thumb

hindlimbs

portion in appendicular region:

- posterior pair
- long
- well adapted for jumping and swimming
- contains: thigh, shank, & pes

thigh

external part of hindlimbs:

- upper leg
- arrow 7

crus

external part of hindlimbs:

- shank / lower leg
- arrow 8

pes

external part of hindlimbs:

- foot
- contains tarsus, metatarsus, 5 fully-webbed toes + prehallux
- arrow 10

tarsus

external part of hindlimbs:

- long ankle
- arrow 9

metatarsus

external part of hindlimbs:

instep

prehallux

6th rudimentary toe

skin on the dorsal side

skin with warty appearance

sex-distinguishing external characteristics

skin pigmentation in jaw, thumb pads, & relative size

male frogs

sex of frog:

- distinct dark pigmentation on skin on the ventral side of the jaw
- generally smaller
- thumb pads are enlarged or swollen

Nuptial pad

- patch of textured skin on male's enlarged thumb
- helps cling to female during amplexus

amplexus

- mating position of frogs
- false copulation
- release sperm to water and not inside the female

female frogs

sex of frog:

- pigments are diffused (NO distinct dark pigmentation)
- relatively bigger
- thumb pads of the inner fingers are NOT swollen

chloroform

- liquid used as an anesthesia for the frog/toad specimen
- rinsed off the dead/preserved specimen before dissection

skeletal system

organ system:

- serves as support or framework for the softer parts of the body
- provide a firm surface for the attachment of muscles used in movement and locomotion
- supplies calcium to the blood
- important site in the formation of blood cells

2 Types of Skeleton

Exoskeleton & Endoskeleton

Exoskeleton

type of skeleton:

- hardened bony or horny structures that develop in the skin and provide external protection to the animal
- poorly developed in frogs
- 2 kinds: chitinous & calcium-carbonate

chitinous exoskeleton

type of exoskeleton:

- made up of chitin
- arthropods, insects, arachnids, crustaceans

calcium-carbonate exoskeleton

type of exoskeleton:

- hard shell
- phylum mollusca: snail, bivalves (scallops)

Endoskeleton

type of skeleton:

- almost entirely of bone and cartilage
- skeleton of frog

Tendon

connective tissue that serves as attachment of (skeletal) muscles and bones

Aponeurosis

broad, flat, and sheet-like tendon

2 Types of Bone Structure

Compact Bone & Spongy Bone

Compact Bone

type of bone structure:

- dense layer from the outside of the bone
- presence of concentric osteons

osteon

- functional unit of compact bone
- made up of lacunae, osteocytes, haversian canal, lamellae, & canaliculi

lacunae

part of osteon:

tiny spaces in the matrix

osteocytes

part of osteon:

bone cells trapped in lacunae

haversian canal

part of osteon:

series of microscopic tubes with blood vessels and nerves

lamellae

part of osteon:

concentric rings of bone

canaliculi

part of osteon:

- passageways for materials to move between cells
- tiny channels between the lacunae

spongy bone

type of bone structure:

- aka Cancellous Bone
- Sponge-like meshwork consisting of trabeculae
- spaces are continuous & occupied by yellow bone marrow & blood vessels

trabeculae

series of branching, overlapping plates of matrix in the spongy bone

spaces in spongy bone

- storage/pockets to hold blood-forming cells (hemopoietic tissue) of bone marrow
- function in weight reduction

yellow bone marrow

adipose tissue around the trabeculae

axial endoskeleton

endoskeleton according to position:

- located at the center or axis of the body
- skull, visceral skeleton, vertebral column, ribs, & sternum

appendicular endoskeleton

endoskeleton according to position:

- located laterally or in the region of the extremities or appendages
- pectoral girdle, pelvic girdle, forelimbs, & hindlimbs

skull

- flattened dorsoventrally
- wider posteriorly and narrow anteriorly
- encloses the brain and sense organs
- includes cranium & the visceral skeleton

cranium

aka braincase

nasal bones

bone in skull:

- flat, triangular-shaped bones on the dorsal surface of the skull behind the nares
- dark blue portion

sphenethmoid

bone in skull:

median, single irregularly shaped bone posterior to nasal bones

frontoparietal

bone in skull:

- 2 long slender flat bones, posterior to the nasal bones
- may be fused so they appear as a single bone
- cover most of the brain
- wide at posterior end, where they join the prootics
- gray portion

prootics

bone in skull:

- joined by frontoparietals
- enclose inner ears
- dark green portion

foramen magnum

bone in skull:

- large opening at the posterior end of the skull where spinal cord passes
- uncolored area under the gray portion

exoccipital

bone in skull:

- surrounding the posterior part of the brain
- bottom gray portion

occipital condyles

bone in skull:

- pair of prominent bones projecting from exoccipital
- light blue portion