Mammal Physiology

Integumentary System

  • Lightweight, waterproof epidermis—variety of environments

    • some have epidermal scales—beaver and rat tails

      • dermal plates—armadillo

  • Epidermis gives rise to hair, glands, nails, scales, hooves, baleen, and horns

  • Hair—arose from specialized mechanoreceptors in early synapsids

    • guard hair—outer, coarser, longer hair for protection

    • Underfur—inner, finer, shorter, for insulation

    • Hair nonliving, replaced

Molting

  • Many molt annually—usually in the fall

  • Some molt twice per year—deer, snowshoe hares, short-tailed weasels

    • some change coloration

    • photoperiod combined with melatonin production initiatives molt

    • geographic variation in molting behavior

Horns and antlers

  • Reproductive behavior, defense, offense

  • True horns—bovine family—cattle, antelope, sheep, goats

    • permanent bony dermal core, epidermal sheath

    • usually not branched, never shed, both sexes

    • grow from base, annual growth rings

  • Antlers—branched, solid, dead dermal bone—Cervidae

    • secondary sex characteristics—males only except Caribou

    • testosterone

    • photoperiod signals replacement

    • start growing in spring, full grown in summer—fall, shed mid-winter

    • velvet—skin with blood vessels feed growing antlers, at full growth velvet rubs off

Glands

  • Mammary

    • modified swet glands produce milk for young

    • hormone prolactin produced by pituitary

    • number of teats equal to maximum litter size or twice the ave

  • Sebaceous—oil glands

    • sebum lubricates hairs

    • antibacterial

  • Scent—numerous widely distributed

    • mark territory

    • attract mates

    • defense

    • considered pheomones if they elicit a specific response from the same species

Skeletal System

  • Skull

    • single pair of temporal fenestrae

    • syxogmatic arach around orbit

    • more complex ear bones than other vertebrates

  • Vertebrae

    • segments: cervical, thoracic, lumbar, sacral, caudal

    • 5 fused sacral vertebrae= sacrum, point of attachment for pelvis

    • ape and human caudal vertebrae fused to form coccyx

Locomotion

  • Plantigrade

    • insectivores, monkeys, apes, humans, bears

    • entire surface of food on ground

    • usually have pentadactyl hands and feet

  • Digitigrade

    • rabbits, rodents, carnivores

    • bear weight of ends of metacarpals and metatarsals

    • wrists and ankles elevated

    • thumb reduced or lost

    • faster than plantigrade

  • Unguligrade

    • weight of body on hooves, modified claws

    • Artiodactyls—cloven hoof, 2 digits function of hoof—deer elk, caribou, giraffes, antelopes, bison, goats, sheep

    • Perissodactyls—1 digit functions as hoof—horses, rhinoceroses

Cardiovascular System

  • 4-chambered heart

  • Variable heart rate

    • 25 bpm elephant

    • 1000 bpm shrews

  • Blood: Erythrocytes, leukocytes, thrombocytes

    • RBCs: non-nucleated, bioconcave discs, carry oxygen

Respiratory System

  • Pharynx > trachea (covered by epiglottis) > bronchi > bronchioles > alveoli

  • Diaphragm

    • muscle that separates pleural cavities from abdominal cavity

    • dome shaped at rest

    • flattens when contracted and enlarges thoracic cavity

    • lowers internal pressure in pleural cavities so air flows into lungs

    • relaxation of diaphragm—air flows out

Digestive System

  • Oral cavity > esophagus > stomach > small inestive > large inestive > rectum > anus

  • Diversity in feeding > diversity in digestive anatomy

Dentition

  • Diphyodont teeth—2 sets

    • millk teeth or deciduous teeth—before or soon after birth

    • permanent or adult teeth—replace milk teeth

  • Heterodont dentition—incisor, canine, premolar, molar

  • Diastema

  • Carnassial teeth

Nervous System

  • Ears

    • Pinna-external, funnels sound to ear canal

    • External auditory meatus—ear canal, sound conveted to eardrum

    • 3 middle ear bones—-malleus, incus, stapes—transmit vibrations from eardrum to inner ear

    • Cochlea—inner ear with hair cells than covnvert mechanical energy into nerve impulses transmitted to brain

  • Echolocation—bats, shrews, whales, seals, manatees

    • animal sonar to locate food, communicate, and move

  • Eyes

    • similar to other aminotes

    • Some mammals colorblind—whales and seals

    • Many mammals have dichromatic vision—dogs

    • Primates have trichromatic vision—blue, green, red

    • Moles and rats—vestigial eyes

  • Nose

    • highly developed olfactory mechanisms

    • large nasal passages

    • especially strong in nocturnal mammals