BIO 102: First Lab Exam

Chapter 1: General Considerations on Animal Form

A.

Descriptive Terms:

C. BILATERAL SYMMETRY exhibited by all vertebrates

Median sagittal plane divides the animal into approximately
identical L-R halves
- Digestive tract only system that doesnt exhibit a symmetrical
relation to median plane in adult stage
D. METAMERISM: regular repetition of body parts along the
anteroposterior axis
Metamere/Segmment/Somite division of the body
1. Homonomous segmentation segmentation
into nearly like segments
2. Heteronomous segmentation various
segments differ from each other
Condition derived from:
i. Loss of segments
ii. Fusion of adjacent segments
iii. Enlargement/reduction of segments
iv. Loss of part in some segments and the retention in others
v. Structural changes among repeated parts

Dorsal back / upper side (posterior in humans)

Ventral under side (anterior in humans)
Lateral side [L & R]
Anterior/Cephalic/Cranial head-end (superior in humans)
Posterior/Caudal tail-end (inferior in humans)
Median middle
Central part of a system nearest the middle
Peripheral part nearest the surface
Proximal near the main mass of the body
Distal away from the main mass of the body
Superficial near the surface
Deep some distance below the surface
B. Planes and Axes:

SAGITTAL PLANE longitudinal axis + dorsoventral axis

Parasagittal any sagittal plane thats not median
FRONTAL PLANE longitudinal axis + mediolateral axis [L-R]
TRANSVERSE PLANE dorsoventral axis + mediolateral axis [L-R]

- Gonads of hemichordates exhibit pseudometamerism

Adult vertebrates internally and heteronomously
segmented animals
E.
F.

CEPHALIZATION: centralization/localization of nervous

structures and functions in the head

Homology and Analogy

HOMOLOGY: intrinsic similarity indicative of common evolutionary
origin
Similarity of anatomical construction
Similar topographical relations with to animal body
Similar embryonic origin
Similarity/identity of specific physiological function or mechanism
ANALOGY: similarity of general function or of superficial appearance
not associated with embryonic origin/development
Convergence analogous structures present striking similarity of
appearance (adaptations)
Divergence - closely related animals differ in general appearance
due to different environments

Chapter 2: Phylum Chordata

A.

Characteristics of Chordates
1. Notochord

2. Dorsal hollow nerve tube

3. Post-anal tail
4. Pharynx pierced by gill slits (embryo/adult)

Ex. Acpinser (sturgeon), Polyodon (paddlefish/ spoonbill)

Subclass Neopterygii w/o spiracle
Order Lepisosteiformes
Ex. Lepisosteus (gar pike) - w/ heterocercal tail
Order Amiiformes w/ homocercal tail
Ex. Amia (bowfin fish)
Order Teleostei (typical bony fishes) w/ homocercal tail; w/o
spiral valve
Ex. Box fish, Pinecone fish

B. Classification of Chordates
Subphylum Urochordata (Tunicates) notochord found in tail of larvae
(absent in adult)
Ex. Pandosia (Sea squirt)
Subphylum Cephalochordata notochord found from head to tail;
(present in adult)
Ex. Amphioxus / Branchiostoma
Subphylum Craniata presence of head case (CRANIUM)
Superclass Agnatha jawless
Class Myxini
Order Myxiniformes narrow-mouthed
Ex. Myxine (hagfish)
Class Cephalaspidomorphi
Order Petromyzontiformes round-mouthed
Ex. Petromyzon (lamprey)

Class Sarcopterygii (lobe-finned fishes)

nostrils opening in to the roof of oral cavity

Superorder Crossopterygii w/ spiracle ; Hyostilic jaw

suspension
Superorder Dipnoi (true lungfishes) w/o spiracle; Autostylic
jaw suspension
Ex. Lepidosiren, Protopterus, Necoratodus
Class Actinopterygii (ray-finned fishes)
no internal openings of nasal sac

Subclass Chondrostei w/ spiracle

Order Polypteriformes lungs opening ventral
Ex. Polypterus
Order Acipenseriformes lungs opening dorsal

Warm-blooded Terrestrial

Cold-blooded Aquatic Animals

Superclass Gnathostomata
Class Chondrichthyes cartilaginous skeleton
Sublcass Elasmobranchii exposed gill slits
Order Carcharhiniformes (sharks)
Ex. Rhizoprionodon
Order Rajiformes (rays & skates) dorsoventrally flat
Ex. Dasyatis, Dipturus
Subclass Holocephali concealed gill slits
Ex. Chimaera (ratfish)

Cold-blooded Aquatic / Terrestrial Animals

Phylum Chordata

Class Amphibia embryo w/o embryonic membrane

with gills in some stages of life history

Order Caudata w/ tail

Ex. Necturus (mud puppy)
Order Anura (frogs & toads) w/o tail
Ex. Rana, Bufo
Class Reptilia embryo w/ embryonic membrane (amnion &
alantois)
w/ thick, dry, scaly skin
gills lacking in all stages of life history

Subclass Anapsida roofed skull w/o temporal vacuities

Order Chelonia
Ex. Chelone (turtles)
Sublass Lepidosauria diapsid skull w/ two lateral temporal
openings
Order Rhyncocephalia teeth fused to jaw (w/o sockets)
Ex. Sphenodon
Order Squamata teeth set in sockets
Ex. Varanus (monitor lizard), Draco, gecko, snakes, skink
Subclass Archosauria diapsid skull w/ two temporal openings;
tending to bipedal gait
Order Crocodilia
Ex. Crocodilus v-shaped snout
Alligator u-shaped snout
Class Aves w/ feathers and uropygial gland
Subclass Neornithes
Ex. Gallus (chicken), Anas (duck), Boteo boteo
Class Mammalia w/ mammary gland
Subclass Placentalia/Eutheria
Order Insectivora smooth brain w/ clavicle and clawed
plantigrade feet; teeth w/ sharp cusps
Ex. Suncus (shrew)

Order Pholidota no clavicle; externally covered w/

imbricated horny scales
Ex. Manis (pangolin)
Order Chiroptera smooth brain w/ clavicle; w/ wing
membranes
Ex. Rousettus (bats)
Order Primates convoluted brain w/ clavicle; hairy
mammals
Order Rodentia w/ clavicle; clawed plantigrade feet,
canines lacking
Ex. Mus (mice), rats
Order Carnivora convoluted brain w/ reduced/absent
clavicleprominent canine
Ex. Felis (cat), Canis (dog)

Chapter 3: Essential Features of Lower Types

Phylum Hemichordata
- Show even greater relationship with invertebrates than
chordates
Ex. Balanoglossus (acorn worm)
Anatomy:

Parts & Functions

Proboscis used in burrowing into the sand
Proboscis Stalk attaches proboscis to inner dorsal surface of collar
Buccal Cavity
Genital Ridges contains the gonads
Gill pores not true gill slits (anterior dorsal side of branchiogenital
region)
Hepatic Caeca have some digestive function
Internal Anatomy (Salient points)
Heart dorsal to the so-called notochord
Central blood sinus blood channel

Glomerulus excretory organ

Phylum Chordata
Subphylum Urochordata (Tunicates)
External Anatomy

Internal Anatomy
Mantle encloses the viscera to which it adheres to
soft body wall beneath test
consists of outer epithelium & inner connective tissue
Pharynx serves as food-catching device & respiratory mechanism

large thin walled bag connected to oral siphon

Atrium cavity between pharynx and mantle
Ganglion constitutes the central nervous system

Found dorsally behind the pharynx

Subphylum Cephalochordata
Ex. Amphioxus / Branchiostoma
Anatomy:
Sagittal Section

Cross sections

Dorsal Fins
Gill Slits
Nasohypoph
yseal Canal

12 pairs

7 pairs

Ends blindly in the

pituitary sac

Continues beyond the

olfactory sac

Buccal
funnel

Anatomy of Lamprey:
Female (x.s)

Male (x.s)

Parts and Functions:

Cirri chemoreceptors used to search for food
Myotomes exactly 60 in number and used for movement (lateral
movement)
Wheel Organ catches food particles
Hatscheks Groove & Pit secretes mucus to aid in catching food
Velum contains the mout of amphioxus
Pharynx serves as food-catching device & respiratory mechanism
Atriopore exit of gametes and liquid waste
Anus exit of solid waste
Notochord serves as skeletal support
Neural Tube central nervous system
Fin Ray supports the dorsal fin
Epibranchial Groove (endostyle) secretes mucus for food particles
to adhere to
Eyes detects light
Pigment Spot unknown function; does not detect light
Relationship of Amphioxus with
a. Balanoglossids
- mode of formation of tongue bars and arrangement of skeletal rods
of gill bars are similar
- wheel organ of amphioxus is homologous with preoral ciliary organ
of balanoglossids
b. Tunicates
- Structures of pharynx (endostyle, peripharyngeal band, &
epipharyngeal groove) are identical w/ tunicates
Subphylum Craniata
Superclass Agnatha
Characterist
ics
Eyes

Myxini
(hagfish)
-

Petromyzon
(lamprey)

Parts and Functions:

Gill Pouches used to respire by pumping water in and out through
the gill slits
Gill lamellae borne on the walls of the gill pouches
Notochord chief axial skeleton of lamprey

Straddled by small separated arches (Lateral Neural

Cartilages)
Branchial Basket supports the gills
Buccal Funnel used to attach to fish as a suction cup
Pericardial Cavity contains the heart
dorsal positioning of olfactory apparatus due to shifting of organs
during development

Larval stage = nasal sacs & hypophysis arise as separate

invaginations on the ventral side

Adult stage = development of buccal funnel brings the nasal

& hypopyhseal invaginations dorsally and fuses them together

Chapter 4: External Anatomy and Adpative Radiation in

Gnathostomes
Class Chondrichthyes
Subclass Elasmobranchii

Order Carcharhiniformes
Ex. Rhizoprionodon (shark)
FUSIFORM (spindle-shaped) body offers little resistance to
water
Body covered in PLACOID SCALES
Fins for locomotion
a.Unpaired (median) fins
i. Anterior and Posterior dorsal fin
ii. Caudal fin = HETEROCERCAL
b.Paired (lateral) fins
i. Pectoral fins
ii. Pelvic Fins

In males: presence of Claspers used in

mating (w/ sperm conducting groove)
Ceratotrichia (dermal fin rays) supports all fins
Presence of Lateral Lines along each side of the body, overlying
the Lateral Line Canal used to detect water vibrations
Head is triangular and somewhat flattened
Rostrum
Mouth bounded by upper and lower jaws
Nostrils allow current of water to circulate through
olfactory sac
Oval eyes w/ immovable upper and lower eyelids
Internal ears connected with the surface of the head via
Endolymphatic ducts
Gill slits communicates with the cavity of the pharynx
(respiration)

Spiracle 1st gill slit

Cloacal aperture (anus) w/ Urogenital papilla seen within
its walls

Cloaca receives urinary and genital ducts, as well as the intestine

Order Rajiformes (skates and rays)

DORSOVENTRALLY FLAT body due to bottom-dwelling habits

Dorsal area covered in

PLACOID SCALES consisting
of an imbedded basal plate
and projecting spine

Ventral is void of scales

Has Pectoral (enlarged) and Pelvic

(reduced) fins; presence of claspers for
males

w/ anus

Head consists of:

dorsal

ventra

Rostrum
Eyes w/o lids
Spiracle for respiration
Mouth
Nostrils
Nasofrontal Process
Oronasal Groove
Gill Slits

Subclass Holocephali
Ex. Chimaera (ratfish)

Has smooth, silvery looking skin and an Opercular opening

(w/c lacks skeletal support)

Has large head and long HETEROCERCAL tail

Males have Frontal Claspers fleshy projections at the

summit of the head

PLACOID SCALES on the head

Class Sarcopterygii (lobe-finned fishes)
Superorder Crossopterygii
w/ spiracle and hyostilic Jaw suspension
Superorder Dipnoi
Ex. Lepidosiren (true lung fish)
trunk covered in CYCLOID SCALES
has a DIPHYCERCAL TAIL
paired fins have retained their primitive position

differ from other fishes

by having internal
nares nasal sacs
opening to the roof of
oral cavity
w/ spiracle and autostylic jaw suspension
Class Actinopterygii
Subclass Chondrostei
Order Polypteriformes
Ex. Polypterus
has a DIPHYCERCAL tail
covered in GANOID SCALES (rhomboid in shape)
Fins
Has small anal fin and long dorsal fin subdivided into
finlets
Paired fins retain primitive position
Operculum supported by bones dorsally and joined ventrally
by a membrane containing Gular Plates forerunners of the
branchiostegal membrane and rays

 w/ spiracles and double nostrils near end of the mouth

Order Acipenseriformes
Ex. Acipenser (sturgeon)
Barbels used as sense organs for food detection
Has double nostrils
Curious mouth bordered with sensory papillae
Has degenerate jaws and teeth
Covered with GANOID SCALES
Has a HETEROCERCAL tail
w/ slitl-like spiracles above each eye and operculum
supported by a single bone
Ex. Polyodon (paddlefish/spoonbill)
Rostrum is expanded into a broad, thin, spatulate structure
provided w/ sense organs for detection of food
has double nostrils and small spiracles
Operculum lacks opercular bones and continues to the
Branchiostegal Membrane w/o rays
Gill rakers found on the gill arches
- Seperates food particles from mud
Has a HETEROCERCAL tail

Branchiostegal membrane supported by branchiostegal rays

Gill arches (4) curved structures, each bearing a gill (w/ gill
rakers)
- Used for respiration
Cavity of pharynx is in communication w/ the exterior
through the Gill slits
Fins are supported by Lepidotrichia
Has an anal opening and urogenital papilla (projecting from
depression behind anal opening)
difference w/ elasmobranchs is that the intestine & urogenital system
of the perch open separately
Adaptive Radiation
a. Body forms and shape:
High, laterally-flattened body = for moving among dense
growths
b. Suckers
Ventral = to attach to rocks
Dorsal = to attach to other fishes (employed by sharks)
c. Enlargement of pectoral fins = for flying
d. Presence of photophores = to attract fish w/c serve as food

Summary:

Subclass Neopterygii
Order Lepisosteiformes
Ex. Lepisosteus (gar pike)
Has hard shining GANOID SCALES and bony operculum
Has very elongated tooth jaws forming a snout
Median and paired fins w/ stout Lepidotrichia bony, flexible,
jointed fin rays
Has a HETEROCERCAL tail
Order Amiiformes
Ex. Amia (bowfin fish)
Has double nostrils and a HOMOCERCAL tail
Covered in CYCLOID SCALES
Median and paired fins supported by Lepidotrichia

Order Teostei (typical bony fishes)

Ex. Box fish & Pinecone fish
Has a HOMOCERCAL tail
Body covered in CYCLOID Scales
Lateral line is present and has large eyes w/o lids
Ears are situated behind the eyes
Head:
Operculum gill cover; supported by opercular bones

Class Amphibia
Order Caudata
Ex. Necturus (mud puppy)
Skin is naked, slimy, and void of scales

 External nares communicate w/ mouth cavity via internal

nares
Has small eyes and internal ears
(3) External gills used for respiration along w/ lungs
- Do not correspond to gills of fishes
Gular fold fold of skin passing transversely across the throat
w/ (2) pairs of appendages correspond to pectoral and pelvic fin
of fishes
Forelimb: upper arm, forearm, wrist (bent downward), & hand
(bent forward)
Brought about by torsion of upper arm
Hindlimb: Thigh, shank, ankle, & foot
In primitive (supine) position
has only 4 digits (1st digit missing)
has flattened tail bordered by tail fin (w/o fin rays)
w/ anus and cloaca
Order Anura
Ex. Rana & Bufo (frogs and toads)
has tympanic membrane (eardrum) covering the middle ear
(5) digits with webbed feet
Class Reptilia
Subclass Anapsida
Order Chelonia
Ex. Chelone (turtle)
Skin shows reptilian cornification
w/ Externals nares allows to breath air w/ only slight
exposure above water
jaws lack teeth but are clothed w/ hard horny beaks
Shell: consists of large horny shields and bony plates
Carapace
Plastron
Lateral bridges connects carapace w/ plastron
Position and torsion of limbs similar to lizards
w/ rounded anus
Subclass Lepidosauria
Order Rhyncocephalia
Ex. Sphenodon
most primitive living reptile internal (skeletal) primitive
characteristics
most noticeable feature: mid dorsal row of spines
Order Squamata
Ex. Varanus (monitor lizard), Draco, gecko, & skink

clothed w/ non-detachable horny scales, plats, and

tubercules
tetrapod body form: head, neck, trunk, and long tail
Head shields enlarged scales/plates on the head
External nares opens to mouth cavity
Has external ears and middle ear (eardrum/tympanic
membrane)
Gular folds = can be extended to form a dewlap
Parietal eye serves some optic function
Skin folds erected/displayed in courtship or battle
Has 5 digits and foot retained primitive position
Femoral pores secretes yellowish waxy material (for
copulation)
Has anus and pre-anal pores

Ex. Snakes
Lacks limbs and eyelids
Poisonous snakes have Pits temperature detectors
Subclass Archosauria
Order Crocodilia
Ex. Alligator & Crocodilia
Have upper (w/ bony support) and lower eyelids; nictitating
membrane
Covered by large horny thickenings
Class Aves
Subclass Neornithes
Ex. Gallus (chicke), Anas (duck), Boteo boteo
Clothed w/ a covering of feathers
Remiges (wings): 1, 2, and
3 (humerals)
Flight feathers
Contour
Retrices (tail)
Feathers
Covert feathers covers general surface area of
the body
Filoplumes (hair feather) hair-like processes
Feather follicles deep pits into w/c contour feathers are set
Head:
Beak jaws incased in horny sheath; teeth absent
Cere cushion-like protuberance at the base of the upper beak
External nares
External auditory meatus narrow passage leading to the
middle ear
External ear elevated skin fold around meatus
Large eyes w/ upper & lower eyelids

Trunk:
Keel of breastbone to w/c the wing muscles are attached
Paired limbs:
a.Wing homologous to forelimbs of other vertebrates
In primitive position when extended
Consists of upper arm, forearm, and fused wrist
&hands
b.Hindlimb clothed partially w/ feathers and partially w/
horny scales
Has (4) digits: 5th is absent
1st is directed posterior for perching
Anus found at the base of the tail
Uropedium where the Uropygial Gland is seen
Secretes oil used for preening feathers
Adaptive radiation:
a. Body form & proportions
b. Relative length and shape of wings
c. Types of beaks and feet -= difference in habitat and food

Trunk
a. Anterior chest/thorax
Teats / nipples the (4-5 pairs) openings of
mammary glands
b. Posterior abdomen
Limbs terminate in clawed digits: 5 in front & 4 behind ( 1st hind
toe is absent)

Prone position crossing of the two bones of forearm

Supine position parallel position of the two bones of

forearm
Walking:
i. Digitigrade walking on digits ( rabbit & cat)
ii. Plantigrade walking on whole sole of foot (man)
iii. Unguligrade walk on their nails ( horses & cattle)
Perineum region w/c includes anal & urogentila openings
Inguinal glands source of characteristic odoriferous
secretions (in rabbits)
In females: opening & labia major together constitutes the
vulva
In males: penis transmitting sperm to female
Scrotum where testes are located
(prepuce/foreskin in cats)
Order Pholidota
Ex. Manis (pangolin)
Has Clawed feet for opening ant nests; long pointed snout
and extensile tongue
Spines are mingled with the fur and a tail is wanting; w/
protective armor
Lays eggs
Milk glands open directly on the skin by several apertures

Class Mammalia
-

Warm blooded
vertebrates
provided with
hair and
Mammary
glands for
nourishing the
young w/ milk

Subclass Placentalia
Order Carnivora
Ex. Felis (cat)
Body is clothed Fur closely set hairs
Whiskers/vibrissae have rich nerve endings that serve as
tactile organs
Head:
Facial region in front of eyes
Cranial region enlarged posterior region
External nares overhung by the mobile nose
Has eyes with upper & lower lids and a nictitating membrane

Pinna long & flexible external fold at the rim of the

external auditory meatus; sound catching device

Adaptive Radiation:
a.Rousettus (bats)
great lateral expansions (wing membranes) = for true flight
large ear pinnae
b.ungulates

hoofs = modified toenails

c. aquatic mammals
blubber = thick layer of fat under the skin to retain body warmth

Chapter 5: General Features of Chordate Development

A. Chordate Eggs and Development
Specimen
Type of Egg
s

Type of Cleavage

Blastula

Gastrula

Fromation of Germ layers,

notochord and neural tube

Germ
Layers:
Ectoder
m&
Entoder
m
Archenteron
(gastrocoel)
primitive
intestine
Blastopore
opening of
archenteron to the
exterior

Anphioxus
&
Mammals

ISOLECITHAL
w/ little yolk, evenly
distributed

HOLOBLASTIC, EQUAL
egg divides and
produces a number of
approximately equal
cells

Blastomeres (cells)
Blastocoel (cavity)

Germ
Layers:
Ectoder
m&
Entoder
m
Archenteron
(gastrocoel)
Blastopore
Yolk Plug enclosed
yolk-bearing cells
Chordamesoderm
roof of archenteron

Coelomic (mesodermal)
sacs
Mesoderm
a. Somatic (parietal)
mesoderm
outer; in contact
with ectoderm
b. Splanchnic mesoderm
inner; in contact with
entoderm
Coelem (body cavity)
cavity of the pouches
Neural Tube primordium
of brain and spinal
cord
Notochord primitive axial
skeleton
Archenteron

Amphibian
s

TELOLECITHAL
w/ moderate amt. of
yolk accumulating in
half of the egg

HOLOBLASTIC,
UNEQUAL
cells withdraw from
the center, producing
blastula w/ reduced
blastocoel and a wall
several layers thick

Animal Hemisphere
(micromere)
contains majority of
protoplasm
Vegetal Hemisphere
(macromere)
contains most of the yolk

Blastocoel

Birds,
Reptiles, &
egg-laying
Mammals

TELOLECITHAL
w/ enormous amt. of
yolk and protoplasm
concentrated on small
disk (Germinal Disk)

MEROBLASTIC
small germinal disk
undergoes cleavage

Blastoderm (disk of cells

on the surface of the yolk)
Blastocoel
slight slit between
blastoderm and yolk

Formation and Development:

in Amphioxus, Mammal, and amphibian eggs
cleavag
Egg cell
e
stage

Invaginati
Blastula
on

Gastrula

Mesoderm
c. Somatic (parietal)
mesoderm
d. Splanchnic mesoderm
Coelom (body cavity)
Notochord
Neural tube
Archenteron

Primitive Streak
represents the formation
of the roof of
archenteron
source of notochord and
mesodermal sheets
Hensens Node
represents blastopore
Neural tube stage
Neural

Germ Layers:
Ectoderm &
Delaminated
entoderm
Archenteron will
disappear

groove stage
Neural plate

In Reptilian and bird eggs

Egg cell
cleavag Blastoder
(Germinal disk)
e
m

Invaginati
Delaminati
on
on

Gastrula

Neural plate stage

Neural tube Stage

Neural Groove stage

Development of Amphibian Egg

Gastrulation

Development of Amphioxus Egg:

Gastrulation

Early Gastrula

Middle Gastrula

Late Gastrula

Neurulation

Neurulation

Neural plate stage

stage

Fate of Germ Layers:

Ectoderm:
Gives rise to neural tube (CNS)
Forms the external layer of the skin and all its derivatives
Gives rise to the sensory part of all sense organs
Lining membrane of all nasal & mouth cavities, anus, glands of skin,
enamel of teeth and lens of the eye
Cranial Nerves & melanophores [from the neural crest]

Neural groove stage

Neural tube

Entoderm:
Primitive intestine
Forms epithelial lining of intestine and all its derivatives:
- Respiratory system: Gill pouches & gills, larynx
- Digestive system: liver, gall bladder & bile duct, pancreas

Mesoderm:

Chapter 6: Comparative Anatomy of the Skin and Exoskeleton

Epimere

Mesoderm
&ducts

Sclerotome (vertebral column)

Dermatome (dermis of the skin)
Myotome (muscles)

Mesomere

Kidneys, reproductive organs

Somatic mesoderm

parietal

pericardium
Hypomere
Splanchnic mesoderm visceral
pericardium
Circulatory system
Somatic mesoderm + Ectoderm = Somatopleure (body wall)
Splanchnic mesoderm + Endoderm = Splanchnopleure (intestinal wall)

Mesothelium parts of the mesoderm w/c dont become

mesenchyme but retain epethilial characteristics
Mesenchyme
Gives rise to all connective tissues of the body including cartilage
and bone
Smooth muscles
Blood cells, blood vessels, lymph vessels & glands
1. Sclerotome mesenchyme cells w/c migrate to a position around the
notochord
2. Dermatome mesenchyme cells w/c migrate to underside of
ectoderm
3. Myotome - separated from each other by myoseptum

A. General Considerations of the Skeleton and Terms

Skeleton includes all of the hardened portions of the bodies of
animals
1. Exoskeleton (external skeleton)
Derived from skin
i. Epidermal = derived from epidermis (ectodermal origin)
ii. Dermal = derived from dermis (mesodermal origin - dermatome)
Forms covering and protective layer outside the body
2. Endoskeleton (internal skeleton)
Derived from innerwall of epimere (sclerotome)
Support & framework of the body and place of attachment for voluntary
muscles
Bone fibrous connective tissue arranged in lamellae, impregnated
with salts, containing bone cells
Dentine chief constituent of teeth
Dentinal tubules
Enamel epidermal in origin (stratum germinativum)
Shiny outer coat of teeth
B. Structure of the Skin
Skin surface covering easily separable from the underlying muscular
layer of body wall
1. Epidermis Outer layer composed of stratified epithelial cells
Outermost layer undergoes KERATINIZATION (flattening and
hardening into a horny stratum)
Stratum corneum keratinized stratum
Stratum Germinativum active portion of the epidermis
that proliferates (Columnar cells)
Stratum Lucidum & Stratum Granulosm (in humans
and birds) seperates the stratum corneum from the
stratum germinativum
2. Dermis Inner layer composed of connective tissue
a. In humans: fibrous connective tissue
Dermal Papillae

Sweat glands long, hollow tubular

glands w/c secrete sweat as means of
lowering body temp.

Sebaceous glands - solid epidermal

ingrowths w/c secrete an oily
substance for lubricating the skin &
hairs ; protection from water

Mammary glands*

b. In frogs:
Statum Laxum next to epidermis;
consisting of loose open connective
tissue
i. Cutaneous glands

really part of stratum germinativum,

invaginated to loose protion of dermis

produces mucous and other protective

secretions
ii.
Chromatophores
(pigment cells)

dark irregular branching cells beneath

the epidermis
Melanophores black protein
pigment (melanin)
Xanthophores yellow to red fatty
pigments
Guanophores reflect light and
produce white, metallic/iridescent
colors (guanine crystals)

Epidermal pigment is usually of diffuse or

granular type; dermal pigment nearly
always inside chromatophores
Stratum Compactum layers of dense, parallel wavy
fibers

C. Exoskeletons
I. Exoskeleton of Fishes
Clothed w/ scales w/c are dermal in origin
1. Placoid Scale characteristic of
elasmobranchs; giving rough texture to skin
(shagreen shark skin)
Homologous w/ vertebrate teeth
Basal Plate & Projecting Spine
2. Ganoid Scale characteristic of Polypetrus,
Acipenser, Polyodon, Lepisosteus
Hard, shiny rhomboid plates
Immovably joined to each other by Peg-andSocket Arrangement
3. Cycloid Scale characterteristic of Dipnoi, Amia, and
Teleosts
Imbricates arrangement

Fluted inner half

Concentric ridges used to determine age and

growth rate of fish

4. Ctenoid Scale

Fluted inner half

Concentric ridges

Teeth
Dermal Fin Rays:
1. Ceratotrichia
Found in elasmobranchs and Holocephali
Slender, flexible unjointed fin rays consisting of fibrous
material
2. Lepidotrichia

Found in Actinopterygii,

Branched, jointed rays composed of bone

Joints have been shown to be homologous with scales of

the same fish
II. Exoskeleton of Reptiles
Clothed in horny exoskeleton marked of into scales and scale-like
areas
Epidermal in origin (thickening of stratum corneum)
Exoskeleton of Turtles
Composed of Scutes (epidermal thickenings) and bony Plates
(dermal structures)
a. Carapace

Dorsal
b.

Ventral
Plastron

Dorsal
Ventral
III. Exoskeleton of Birds
Clothed in feathers on the greater part of the body, scales & claws on
the feet, and horny beaks (epidermal in origin)
No dermal exoskeleton
Feathers homologous to reptilian scales
a. Down Feathers (Plumules)
Constitute fluffy covering of young birds and bases of
contour feathers in adult birds
Development of feather resembles that of reptilian
scales which involves a nutritive dermal papilla and an
epidermal thickening
Quill
Barbs (w/ hooks)
Barbules
b. Contour Feathers
Common type of feather w/c covers the bodies of birds

Difference in development of down feathers and contour

feathers:
Plumules = barbs spring in a circle from the top of the
quill
Contour feathers = barbs spring from the sides of the
quill
c. Hair Feathers (Filoplumules)
Visible on the plucked bird
Consists of:
Shaft
Barbs
Barbules
Pterylae (feather tracts) areas with feathers
Apterylae areas without feathers
IV. Exoskeleton of Mammals
Exoskeleton primarily consists of hair
Hair (epidermal origin)

Hair follicle pit in the skin

Root part of the hair inside the follicle

Inner root sheath white coat w/c clings to the roots of

hairs when pulled

Shaft exposed part of hair

Cuticle surface layer of hair

Cortex between cuticle and medulla

Medulla central strand of degenerate material

Types of hairs:
Facial vibrissae large tactile hairs on the face
Bristles found in spiny ant-eaters
Guard hairs coarse hair scattered on fur
Aristate hairs smaller, numerous w/ thickened flattened hairs
Wool/fur fine, short, wavy hairs
Scales of mammals
- Armor composed of both epidermal scutes and dermal plates
(like turtles)
Claws, nails, hoofs, and horns
- Composed of compressed layers of stratum corneum
- Covers the last joint of the digit (phalanx)
- Claws, Nails and Hoofs
Nails:

Claws:

Hoofs:

True Horns and Antlers

True horns epidermal outgrowths
hollow
Antlers dermal outgrowths attached to frontal bone