Zoology Lab 02: External Anatomy, Histology, and Skeletal and Muscular Systems of the Frog and Toad

Comprehensive review flashcards covering frog and toad integumentary histology, external anatomy, sexual dimorphism, axial and appendicular skeletal structures, and major muscles.

Based on the provided histological section of amphibian skin, what are the primary layers of the epidermis and dermis?

The epidermis consists of the stratum corneum, stratum spinosum, and stratum germinativum; the dermis consists of the outer stratum spongiosum (stratum laxum, containing mucous and granular/poison glands) and the inner stratum compactum.

How does the skin and body morphology of a toad compare to that of a frog?

A toad's skin is much drier, bumpier, and warty, whereas a frog has much slimier skin and a slender body.

What is the stratum corneum and what occurs to it during ecdysis or molting?

It is the outermost stratified squamous epithelium layer composed of flattened dead cells; it is the hardened or cornified layer that is constantly removed when the toad sheds its skin.

What characterizes the stratum germinativum layer of the epidermis?

It is the innermost epidermal sublayer consisting of a living and growing layer of stratified epithelial tissue where chromatophores (pigment-bearing cells) are visible.

How can the poison gland and mucous gland be distinguished histologically within the stratum spongiosum?

The poison gland is darker and contains a visible granular substance inside, while the mucous gland possesses an open space inside where mucus is stored.

Which primary anatomical directions and body planes are illustrated in this standard anatomical diagram?

It illustrates the dorsal, ventral, anterior, and posterior directions, along with the median/sagittal (longitudinal) plane, transverse (cross) plane, and dorsal/frontal plane.

How are the sagittal, transverse, and frontal planes defined in bilateral animals?

The median/sagittal plane divides the body into equal right and left halves with a mirror image; the transverse (cross) plane divides the body into anterior (upper) and posterior (lower) halves; and the dorsal/frontal plane divides the body into dorsal and ventral portions.

What are the structures and functions of the frog's nictitating membrane and tympanic membrane?

The nictitating membrane is a transparent or translucent third eyelid that protects the eyes and provides moisture underwater; the tympanic membrane is a hard, round structure that serves as the eardrum for auditory reception.

How many digits does a frog or toad have on its forelimb, and what is the prepollux?

The forelimb has $4$ digits, and the prepollux is the rudimentary thumb.

What external characteristics distinguish a male frog from a female frog as shown in the ventral comparison?

Male frogs exhibit distinct dark pigmentation on the skin near the angles of the jaw and a swollen/enlarged nuptial thumb used during amplexus, whereas female frogs have diffused pigmentation, non-swollen thumbs, and are generally larger.

What is the most accurate basis for confirming whether an individual is male or female?

Examination of the urogenital system.

What two types of teeth are found in the oral cavity of the toad/frog?

Maxillary teeth (spiky, rubberized structures along the upper jaw margin) and vomerine teeth (a pair of flat, wing-shaped structures forming an inner zig-zag row on the roof of the mouth).

What are the microscopic components of compact bone tissue?

Osteocytes trapped in spaces called lacunae arranged in concentric rings called lamellae around Haversian canals (housing blood vessels and nerves), interconnected by microscopic channels called canaliculi.

What are trabeculae and what is their role in spongy (cancellous) bone?

Trabeculae are a series of branching, overlapping plates of matrix that create interconnecting cave-like spaces to hold hemopoietic tissue (blood-forming cells) and blood vessels, functioning in storage and weight reduction.

Identify the cranial bones and sutures visible on the dorsal surface of the frog skull.

Premaxillae, maxilla, nasal bones, sphenethmoid, fronto-parietal bones separated by the median dorsal suture, prootic, squamosal, quadratojugal, exoccipital, occipital condyles, and the foramen magnum.

What is the single dagger-shaped bone on the ventral floor of the frog cranium, and what is the longest bone of the lower jaw?

The single dagger-shaped bone is the parasphenoid; the longest bone of the lower jaw is the angulo-splenial (which features a coronoid process for muscle attachment).

Identify the skeletal elements composing the frog pectoral girdle and sternum.

Episternum, omosternum, clavicle, scapula (with the fenestra), suprascapula, glenoid fossa (socket articulating with the humerus head), coracoid, epicoracoid, mesosternum, and xiphisternum.

What distinctive bone fusion is found in the forearm of the frog and toad?

The radius and ulna are fused together into a single element called the radio-ulna.

Identify the structures present on the frog's atlas and typical trunk vertebrae.

The atlas ($1\text{st}$ vertebra) features anterior concavities for articulation with the occipital condyles; typical trunk vertebrae ($2\text{nd}$ to $8\text{th}$) possess a neural spine, neural arch, postzygapophyses, neural canal, and centrum.

What constitutes the $9\text{th}$ and $10\text{th}$ vertebral elements of the frog backbone?

The $9\text{th}$ vertebra is the sacral vertebra (with enlarged transverse processes), and the $10\text{th}$ vertebral element is the urostyle, which terminates the column and bears an elevated dorsal ridge called the keel or carina.

Identify the three fused bones and the articulation socket of the frog pelvic girdle.

The ilium, ischium (with ischiac symphysis), and pubis (with pubic symphysis), which converge to form the circular acetabulum where the head of the femur attaches.

What bones make up the proximal tarsals and what is the phalangeal formula of the frog hindlimb?

The proximal tarsals are the elongated fibulare (calcaneum) and tibiale (astragalus); the phalangeal formula for the $5$ toes is $2\text{-}2\text{-}3\text{-}4\text{-}3$ (the pre-hallux is not counted).

How are anatomical origin, insertion, belly, heads, and slips defined for skeletal muscles?

The origin is the fixed or stationary attachment point; insertion is the movable attachment point; the belly is the fleshy region between them; heads are multiple origins; and slips are multiple insertions.

What cutting pattern and anatomical surface are recommended when skinning a frog?

An "I" pattern cut on the ventral surface to allow pinching and prevent cutting the underlying muscles.

What are the anatomical locations of the longissimus dorsi and the gastrocnemius muscles?

The longissimus dorsi is the prominent longitudinal muscle along the dorsal midline extending down to the gluteus; the gastrocnemius is the largest calf muscle located on the posterior aspect of the shank (crus) between the knee and ankle.

What is the longest muscle in the frog's hindlimb, and what midline structure separates the rectus abdominis muscles?

The longest muscle in the leg is the sartorius; the midline vertical connective tissue strip separating the rectus abdominis muscles is the linea alba.