Class Mammalia
Phylum Chordata
General Characteristics
1. Hair or fur: 
a. keratinized derivative of the skin
b. uniquely mammalian
c. hair coat also called a pelage.
1. kinds of hair:
a. guard hairs ,function: protects the
wooly hair
b. wooly hairs function: insulation
Glands
1. sebaceous: secretes
oil
that

lubricates and waterproofs the skin
and hair.
2. sweat: evaporation of salt, urea
and water.
3. scent: secrete pheromones which
may be used for defense, species and
sex recognition and territorial
behavior.
4. mammary: secretes milk.
Teeth

a. homodont: teeth are uniformly conical
(reptiles)
b. heterodont: teeth are specialized for
different functions (mammals)
1. incisors: for gnawing and nipping
2. canines: catching, gripping and tearing
3. premolars: for shearing and slicing
4. molars (bicuspids and tricuspids): for
grinding
Structure of Tooth

1. enamel- hard outer covering
2. dentin- largest portion of the tooth
3. cement- covers part in the jaw
4. pulp- nerves, blood vessels, and connective
tissue
5. crown- top of the tooth
6. Neck
7. root(s)

 Tooth
Numbers of Teeth

8 incisors, 4 canines, 8 premolars, 8
molars, 4 wisdom teeth (molars)
mammals without teeth:
whalebone whales, monotremes
and anteaters
Development

1.
Monotremes: oviparous (egg laying).
2. Marsupials: young develop in a pouch,
young are nourished by “uterine milk”.
3. Placentals: young are nourished by the
mother’s blood through a placenta.
a. altricial- born without hair
b. precocial- born with hair

Internal Anatomy

Skeleton
a. seven neck vertebrae
b. two occipital condyles (synapsid skull)
c. trunk divided into thoracic and lumbar
regions
d. four limbs (except whales and dolphins)
e. skeleton a combination of bone and
cartilage
Respiratory and
Circulatory Systems

a.Lungs
b. Diaphram
Temperature regulation
a. endothermic
 Circulatory
a. 4-chambered heart
b. b. systemic (whole body)and pulmonary
loops (lungs)
Excretory System

a. metanephric kidneys- produce urea
b. Ureters
c. urinary bladder
d. urethra
Nervous System

a. enlargement of the cerebral
hemispheres
b. enlargement of the cerebellum
c. well developed sense of touch,
associated with the hair follicles
d. well developed senses of smell, sight,
and hearing
Reproductive System
a. internal fertilzation
b. most are viviparous (live birth) No eggs!
c. female mammals undergo an estrus cycle
(cycle where the ova (egg)matures and is
released)
1. monoestrus: single yearly estrus cycle
2. diestrus: twice yearly estrus cycle
3. polyestrus: estrus cycles repeat often
d. varied gestation period-length of time young
develop within the female reproductive tract.
Lactation

(only mammals have the ability to nurse young)

a. two hormones control milk production
1. estrogen is released by the pituitary gland during
labor and causes milk production in alveoli.
2. progesterone is released by the pituitary gland
during labor and causes milk production in laciferous
ducts.
b. nursing stimulates the pituitary which in turn
continues to stimulate the release of both hormones