ANIMAL ORGANIZATION,

HOMEOSTASIS, AND THE

INTEGUMENTARY SYSTEM Chapter 31

Tissue

• Tissues are groups of similar cells performing similar functions

• Organs are groups of tissues performing a specialized function

• A group of organs that all work toward the same overall function

but perform different steps are called an organ system

• Multiple organ systems work together to make up an organism.

• There are four major tissue types in vertebrates. • Epithelial Tissue

• Connective Tissue

• Muscle Tissue

• Nervous Tissue

Epithelial Tissue Epithelial tissue covers body surfaces, lines body cavities, and

forms glands

Epithelial tissue is characterized by its two sides of cells

One side of epithelium is exposed to the environment (outer skin and body

cavities)

The other side is attached to a chaotic matrix of thin membranes giving it

both flexibility and rigidity.

There are three types of epithelial tissue Squamous: flat cells (good for nutrient exchange and sensory transfers)

Cuboidal: cube-shaped cells (Good for secretion, absorption and insulation)

Columnar: pillar or column cells (Good for protection and support)

Epithelium can be simple or stratified

Simple: a single layer of cells

Stratified: layers piled on top of each other, some which do not touch a membrane

Epithelial Tissue

• Epithelial tissues function in protection, gas exchanges, and

absorption of nutrients.

• If the epithelial tissue secretes a product, it is glandular • Exocrine glands secrete products into ducts or cavities (Sweat, saliva)

• Endocrine glands secrete products into bloodstreams (Pituitary, Adrenal)

• In terrestrial vertebrates, epithelium contains keratin, which

protects skin from water loss.

• Epithelium are packed tightly and joined together in three ways

(remember chapter 5?) • Tight junctions: plasma membrane proteins bind neighboring cells

• Adhesion junctions: cytoskeleton join internal plaques of neighboring cells

• Gap junctions: plasma membrane channels bind neighboring cells

Connective Tissue

• Connective Tissues bind and support body parts, fill

spaces, store fat, and form blood cells

• Fibroblast cells • Fibroblast matrix cells give epithelial tissue a protective covering

• Fibroblast collagen cells give them flexibility and strength

• Looser fibroblasts attach epithelial tissue to internal organs

• Denser fibroblasts form tendons (connecting muscle to bone) and

ligaments (connecting bones to other bones)

Connective Tissue

• Adipose Tissue (Body fat) • Adipose tissue insulates the body and provides padding.

• Cartilage

• Cartilage is a bone alternative that absorbs impact well

• In human fetuses and babies, cartilage is found in soft heads, arms and

legs.

• In human adults cartilage is found at the ends of long bones, the nose, the

ear, and respiratory ducts

• Cartilage is remarkably strong yet flexible, so it’s helpful in areas where we

need some bendability while maintaining sturdiness

Connective Tissue

• Bone • Hard, compact bone contain bone cells called osteocytes

• Osteocytes are arranged in long canals throughout the bone

• Inside these canals are nerve fibers and blood vessels which supply

nutrients to the bone (which is why it’s painful when you fracture a bone)

• The ends of bone contain spongy bone, which are osteocytes separated by

irregular spaces of red bone marrow

• Blood

• There are two blood cells in vertebrates: red blood cells (carry oxygen) and

white blood cells (immune system)

• Blood cells are suspended in a liquid called plasma, which is 94% water but

also contains food and nutrient products, platelets and clotting factors,

hormones, CO2 products, electrolytes and proteins.

• BLOOD55% Plasma, 44% RBC’s, 1% WBC’s.

Muscle Tissue

• Muscle tissues cause body parts to move (not merely

allow for movement)

• All muscles move through the coordination of actin and

myosin (more in chapter 39)

• Skeletal muscle (Voluntary muscle) • Skeletal muscle is attached by tendons to the bones of the skeleton, forcing

body parts to move

• Skeletal muscle is controlled by the organism and faster than other types of

muscle

• Skeletal muscles cells are long and smooth, sometimes even extending the

entire length of the muscle

• The placement of actin and myosin gives skeletal muscle a striated, layered

“fish skeleton” appearance

Muscle Tissue

• Smooth Muscle (Visceral Muscle) • Smooth muscle forms an irregular pattern without any striations

• Smooth muscle is involuntary and controlled by hormones and the brain.

• Smooth muscle is found in the walls of viscera (intestine, stomach, etc) and

blood vessels

• Smooth muscle contracts more slowly than skeletal, but for longer periods

of time

• Cardiac Muscle

• Cardiac muscle make up the heart walls

• Coordinated contraction of heart muscles pump blood and account for

heartbeats

• Cardiac muscles are separated by folded plasma membranes called

intercalated disks which allow electrical currents to travel through

Nervous Tissue • Nervous tissue responds to stimuli and transmits impulses from

one body part to another

• Neurons (3 parts of a neuron)

• Dendrites of neurons receive messages and direct them toward the cell

body of the neuron (1,000 per cell)

• Cell bodies contain the majority of cytoplasm, organelles, and the nucleus

of the neuron cell

• The axon conducts messages from the neuron to adjacent cells (1-3 per

cel)

• Fibers of axons bound by connective tissues are called nerves

• Nerves function in sensory input, integration of data, and motor

outpit.

• Except for reflexes, sensations are only measured and

calculated in the brain. Nerves must send or receive messages

to/from the brain for a sensation to be registered by an organism

• If not, this is called paralysis

Nervous Tissue

• Neuroglia

• Neuroglia outnumber neurons 10-1 and are the majority of the brain’s volume.

• Not much is known about their direct input into brain activity except for their role in support and nourishing neurons • Microglia: engulf bacterial and cellular debris

• Astrocytes: provide nutrients to neurons and produce a hormone known as glia-derived growth factor

• (Currently a target for brain researchers attempting to cure neuronal diseases in the brain)

• Oligodendrocytes: form myelin, which insulates neurons and makes the process of conduction faster and more efficient.

Integumentary System

• The integumentary system is made up of the epithelial tissue,

hair follicles, oil and sweat glands, and sensory receptors

• The integumentary system plays a role in cushioning the body

from physical trauma, preventing pathogen invasion and water

loss.

• Skin has two regions, the epidermis and the dermis.

• Epidermis is the outer, thinner region of the skin

• Flattened, hardened cells that are dead or near-death

• The thicker the skin, the more keratin is present (palm of hand)

• Specialized cells called melanocytes produce melanin, which provide

pigmentation and protect against UV light

• Nail roots form large cells filled with keratin that expand out of the

epidermis

Integumentary System

• Dermis • Thicker and deeper than the epidermis and containing elastic and collagen

fibers

• Hair roots are located here and form thick epithelial cells surrounded by an

oily mucus that lubricates the hair and skin

• If the mucus fails to discharge, it forms a whitehead or blackhead

• Sweat glands are located here

• Sensors for touch and heat are located deep in the dermis to prevent

against loss of the nerve endings if the epidermis is damaged.

• In some areas (palms, lips, fingertips, tongue, nipples and genitalia)

specialized touch sensors exist in high quantities.

• The more sensors exist, the more specific and intense the signals that

the brain receives.

Homeostasis

• Homeostasis is the act of maintaining an internal

environment despite changes to the external

environment • The digestive system slowly introduces nutrients to ensure that cells never

go malnourished

• The respiratory system works nonstop to maintain the oxygen levels of the

blood

• Hormones regulate temperature and pH levels of your body

• Every body system works to balance out it’s individual

homeostatic needs

Body Cavities

• There are two main body cavities: the smaller dorsal

cavity and the larger, ventral cavity

• The dorsal cavity contains the brain and the spinal cord

• The ventral cavity is split by the diaphragm and pelvis. • Above the diaphragm is the thoracic cavity (the chest) containing the heart

and lungs

• Below the diaphragm is the abdominal cavity, containing stomach, liver, gall

bladder, intestines, pancreas, spleen, and kidneys.

• The pelvic cavity contains the anus, bladder, and reproductive organs

Negative Feedback • Negative feedback ensures a homeostasis system

always returns to a specific variable or set point

• Feedback systems are a series of three steps: • Sensor: detects a change in the internal environment

• Regulatory center: activates an “effector.”

• Effector: brings the change back to normal

• Example: • Sensor: cells recognize a rise in glucagon, a product that appears when

glucose levels are high

• Regulatory center: the liver releases insulin

• Effector: insulin lowers blood glucose levels

• In contrast, positive feedback—which is rarer—allows for a

series of steps to progress rather than return to a starting point

(ex. Pregnancy)

Homeostasis Example: Body Temperature

• The hypothalamus, a portion of the brain which

regulates the internal temperature of the body, is

triggered by the blood temperature • When the temperature is low, nerves direct the cells of the skin to constrict,

conserving heat

• If it falls lower, messages are sent to the skeletal system to begin shaking, or

shivering

• When the temperature is too high, the nerves direct the skin cells to dilate,

allowing for more heat loss.

• Sweat glands are also activated

• In these ways the body is constantly altering itself to

account for environmental changes