Transcript connective tissue

Introduction to Tissues, Organ
Systems, and Homeostasis
Chapter 4
Homeostasis
• Stable operating conditions in the
internal environment
• Brought about by coordinated activities
of cells, tissues, organs, and organ
systems
Tissue
• A group of cells and intercellular
substances that interact in one or more
tasks
• Four types
Epithelial tissue
Muscle tissue
Connective tissue
Nervous tissue
Organs
• Group of tissues organized to perform a
task or tasks
• Heart is an organ that pumps blood
through body
• Heart consists of muscle tissue, nervous
tissue, connective tissue, and epithelial
tissue
Organ Systems
• Organs interact physically, chemically,
or both to perform a common task
• Circulatory system includes the heart,
the arteries, and other vessels that
transport blood through the body
Epithelial Tissue
• Lines the body’s surface, cavities,
ducts, and tubes
• One free surface faces a body fluid or
the environment
basement
membrane
simple
squamous
epithelium
connective tissue
Simple Epithelium
• Consists of a single layer of cells
• Lines body ducts, cavities, and tubes
• Cell shapes:
Squamous
Cuboidal
Columnar
Stratified Epithelium
• Two or more layers thick
• Functions in protection, as in skin
• Cells in the layers may be squamous,
columnar, or cuboidal
Glands
• Secretory organs derived from
epithelium
• Exocrine glands have ducts or tubes
• Endocrine glands are ductless
Cell Junctions
• Tight junctions
prevent leaks
• Gap junctions
connect abutting
cytoplasms
• Adhering junctions
cement cells
together
Connective Tissue
• Most abundant tissue in the body
• Cells are scattered in an extracellular
matrix
• Matrix is collagen and/or elastin fibers in a
polysaccharide ground substance
Soft Connective Tissues
Loose
connective
tissue
Dense, irregular
connective
tissue
Dense, regular
connective
tissue
Specialized
Connective Tissues
Cartilage
Bone
Adipose tissue
Blood
• Classified as a connective tissue
because blood cells arise in bone
• Serves as the body’s transport medium
• Red cells, white cells, and platelets are
dispersed in a fluid medium called
plasma
Muscle Tissue
• Composed of cells that contract when
stimulated
• Helps move the body and specific body
parts
Three Types of Muscle
• Skeletal muscle
• Smooth muscle
• Cardiac muscle
Skeletal Muscle
• Located in muscles that
attach to bones
• Long, cylindrical cells are
striated
• Cells are bundled closely
together in parallel arrays
Smooth Muscle
• In walls of many internal
organs and some blood
vessels
• Cells are not striped and
taper at the ends
Cardiac Muscle
• Present only in the heart
• Cells are striated and
branching
• Ends of cells are joined by
communication junctions
Nervous Tissue
• Detects stimuli, integrates information,
and relays commands for response
• Consists of excitable neurons and
supporting neuroglial cells
Neurons
• Excitable cells
• When stimulated, an electrical impulse
travels along the plasma membrane
• Arrival of the impulse at the neuron
endings triggers events that stimulate or
inhibit adjacent neurons or other cells
Neuroglia
• Constitute more than half of the nervous
tissue
• Protect and support the neurons, both
structurally and metabolically
Replacement Tissues
• Artificial skin
• Bioengineered cartilage and bone
• Organoapatites and coral to repair bone
Stem Cells
• Have the potential to develop into
different kinds of mature cells
• Embryonic cells most useful but use of
embryos as source is controversial
• Some adult tissues also may provide
stem cells
Membranes
• Epithelial tissue membranes
– Mucous membranes
– Serous membranes
– Cutaneous membrane
• Connective tissue membranes
– Synovial membranes
Major Organ Systems
• Integumentary
• Lymphatic
• Muscular
• Respiratory
• Skeletal
• Urinary
• Nervous
• Circulatory
• Endocrine
• Reproductive
Major Body Cavities
• Cranial cavity
• Spinal cavity
• Thoracic cavity
• Abdominal cavity
• Pelvic cavity
Planes of Symmetry
Frontal plane
(aqua)
Transverse plane
(yellow)
Midsagittal plane (green)
Primary Tissues
• In vertebrate embryos, cells become
arranged to form three primary tissues
Ectoderm
Mesoderm
Endoderm
• These give rise to all adult tissues
Functions of Human Skin
• Protects the body from injury,
dehydration, UV radiation, and some
pathogens
• Helps control temperature
• Receives some external stimuli
• Produces vitamin D
Structure of Human Skin
• Part of body’s
integument
• Two layers
– Outer epidermis
– Inner dermis
• Atop a layer of
hypodermis
Epidermis
• Stratified epithelium
• Grows from bottom upward
• Most abundant cells are keratinproducing keratinocytes
• Melanocytes produce the brown
pigment melanin
Dermis
• Dense connective tissue with many
elastin and collagen fibers
• Includes blood vessels, lymph
vessels, and receptor endings of
sensory nerves
Sweat Glands
• Arise from epidermal cells
• Composition of sweat
– 99% water, with dissolved salts, trace of
ammonia (waste product)
• Controlled by sympathetic nerves
Oil Glands
• Also called sebaceous glands
• Derived from epidermal cells
• Secretions lubricate and soften hair and
skin; also kill many surface bacteria
• Acne occurs when bacteria infect oilgland ducts
Hair
• Root is embedded in skin
• Cells near the base of root divide, push
cells above them upward
• Hair follicles nourished by the dermis
• Shaft of dead cells extends above the
skin surface
UV Damages Skin
• UV light stimulates melanin production
in skin; produces a tan
• Tan is the body’s way of protecting
itself against UV
• Prolonged sun exposure causes
elastin fibers to clump, skin to age
prematurely, increases risk of cancer
Body Fluids
• The human body contains about 15 liters
of fluid
• Fluid outside of cells is extracellular fluid
– Interstitial fluid lies between cells
– Plasma is the fluid portion of the blood
Fluid Balance
• Changes in extracellular fluid cause
changes in cells
• The component parts of every animal
work to maintain a stable fluid
environment for living cells
Homeostasis
• Stable operating conditions in the
internal environment
STIMULUS (input into the system)
RECEPTOR
(e.g., free
nerve ending
in the skin)
INTEGRATOR
(such as
the brain)
EFFECTOR
(a muscle
or a gland)
Response to the stimulus leads to change.
Change is “fed back” to the receptor.
RESPONSE
(system’s
output)
Negative Feedback
• Some activity alters a condition in the
internal environment
• Alteration triggers a response
• Response reverses the altered condition
Positive Feedback
• Some activity alters the internal
environment
• The alteration triggers a response
• The response intensifies the change in
the internal condition