Lecture 3- Body Organization and Tissues **not completed**

Organization of the body

chemicals— cell— tissues— organs— organ systems— organism

integumentary system

external covering of the body- protection, moisture retention, sensory information

comprised of skin and its derivatives (sweat and oil glands), hair (wool, fur), and nails (claws, hooves)

functions:

• physical protection

• sensory information (cutaneous receptors)

• secretion/excretions

• storage

• body temperature regulation

• communication

skeletal system

support, protection, movement, blood cell formation, and mineral storage

• connective tissue

muscular system

movement, posture, heat generation

• smooth muscle —> movement of fluids

nervous system

coordinates animals interactions with internal and external environment

endocrine system

hormone production to maintain homeostasis

cardiovascular system

blood vessels and heart, transport nutrients and waste

lymphatic system

return excess fluid to blood, immunity

• lymph nodes

respiratory system

gas exchange to provide body oxygen

digestive system

nutrient acquisition, immune function

urinary system

elimination of waste, maintaining fluid balance

• kidney + bladder

reproductive system

production of offsprings

epithelium tissue

covers a surface, protection, glandular activity

• skin, etc

protection, secretion, absorption

named for:

• number of layers

• shape of cells

• processes

connective tissue

provides support, storage, protection

• “connect” things together

• ex: bone, cartilage, adipose tissue, blood, loose connective tissue

cells embedded in extracellular matrix (ECM)- noncellular material surrounding cells

muscle tissue

skeletal, smooth, cardiac

glands

modified epithelial cells

• secretory (stays in the body) and/or excretory (leaves the body) component

types of glands

• unicellular: individual secretory cell interspersed with other epithelial cells (ex: mucus?)

• multicellular: many secretory cells folded to form a more complex gland shape (ex: skin)

joining epithelial cells

occluding junctions or tight junctions

• “Smashing membranes together, keeping them tightly together

anchoring junctions

communicating junctions- ex: Gap Junctions

skin

thin outermost layer; stratified squamous epithelium, base cells divide and keratinize as they push upward

4 layers:

• stratum basale: single layer of dividing cells; melanocytes may be present

• stratum granulosum: keratinization begins

• stratum lucidum: cells lose nuclei

• stratum corneum: outermost layer, cells are dead, flattened, and fully keratinized

keratin

protein deposited in epidermal cells- protection and water resistance

• claws, nails, hooves, horns, hair, feathers

exocrine glands

sweat, sebaceous, mammary

dermis

layer of skin underlying epidermis

• connective tissue with collagen and elastin

• blood supply

• nerves

hair follicles, glands lie within this layer, but are formed from epidermal cells

hypodermis

layer of loose connective tissue and fat underneath skin

elastic fibers

where subcutaneous injections are given

sebaceous glands

open into the base of hair follicles, secrete an oily substance called sebum

• antiseptic quality, waterproofs coat and moisturized skin

• modified versions may produce pheromones

sweat glands

secrete water with salt to cool animals off

• only active on the nose and footpads of dogs and cats

• humans, horses, hippos- all over the body

Fur/Hair

keratinized structure produced by a hair follicle

• shaft - visible part of hair

• root - part that lies within follicle

follicle originates from epidermal cells that descent into dermis

hair growth is cyclical, hair will shed and new hair grows in its place

shedding - influenced by temperature and day length

• in companion animals, disrupted by housing

guard hairs

thick, long, stiff hairs that form protective outer coat

wool hairs

soft undercoat, thinner, shorter hairs

• several can originate from one follicle

• thickness (or presence) varies between animals

Tactile hairs

whiskers

• thicker than guard hairs

• follicle surrounded by nerve endings that respond to touch or movement

piloerection

contraction of the arrector pili muscle

raises hair from resting position

stimulated by cold temps, response to threat