1. Introduction to Tissues, Organ Systems, and Homeostasis
Chapter 4

2. Homeostasis Stable operating conditions in the internal environment
Brought about by coordinated activities of cells, tissues, organs, and organ systems

3. 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

4. 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

5. 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

6. Epithelial Tissue Lines the body’s surface, cavities, ducts, and tubes
One free surface faces a body fluid or the environment
simple
squamous
epithelium
basement
membrane
connective tissue

7. Simple Epithelium Consists of a single layer of cells
Lines body ducts, cavities, and tubes
Cell shapes:
Squamous
Cuboidal
Columnar

8. Stratified Epithelium
Two or more layers thick
Functions in protection, as in skin
Cells in the layers may be squamous, columnar, or cuboidal

9. Glands Secretory organs derived from epithelium
Exocrine glands have ducts or tubes
Endocrine glands are ductless

10. Cell Junctions Tight junctions prevent leaks
Gap junctions connect abutting cytoplasms
Adhering junctions cement cells together

11. 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

12. Soft Connective Tissues
Loose connective
tissue
Dense, irregular connective tissue
Dense, regular connective tissue

13. Specialized Connective Tissues
Cartilage
Bone
Adipose tissue

14. 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

15. Muscle Tissue Composed of cells that contract when stimulated
Helps move the body and specific body parts

16. Three Types of Muscle
Skeletal muscle
Smooth muscle
Cardiac muscle

17. Skeletal Muscle Located in muscles that attach to bones
Long, cylindrical cells are striated
Cells are bundled closely together in parallel arrays

18. Smooth Muscle In walls of many internal organs and some blood vessels
Cells are not striped and taper at the ends

19. Cardiac Muscle Present only in the heart
Cells are striated and branching
Ends of cells are joined by communication junctions

20. Nervous Tissue
Detects stimuli, integrates information, and relays commands for response
Consists of excitable neurons and supporting neuroglial cells

21. 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

22. Neuroglia Constitute more than half of the nervous tissue
Protect and support the neurons, both structurally and metabolically

23. Replacement Tissues Artificial skin Bioengineered cartilage and bone
Organoapatites and coral to repair bone

24. 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

25. Membranes Epithelial tissue membranes Connective tissue membranes
Mucous membranes
Serous membranes
Cutaneous membrane
Connective tissue membranes
Synovial membranes

26. Major Organ Systems Integumentary Muscular Skeletal Nervous Endocrine
Lymphatic
Respiratory
Urinary
Circulatory
Reproductive

27. Major Body Cavities Cranial cavity Spinal cavity Thoracic cavity
Abdominal cavity
Pelvic cavity

28. Planes of Symmetry Frontal plane (aqua) Transverse plane (yellow)
Midsagittal plane (green)

29. Primary Tissues
In vertebrate embryos, cells become arranged to form three primary tissues
Ectoderm
Mesoderm
Endoderm
These give rise to all adult tissues

30. 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

31. Structure of Human Skin
Part of body’s integument
Two layers
Outer epidermis
Inner dermis
Atop a layer of hypodermis

32. Epidermis Stratified epithelium Grows from bottom upward
Most abundant cells are keratin-producing keratinocytes
Melanocytes produce the brown pigment melanin

33. Dermis Dense connective tissue with many elastin and collagen fibers
Includes blood vessels, lymph vessels, and receptor endings of sensory nerves

34. Sweat Glands Arise from epidermal cells Composition of sweat
99% water, with dissolved salts, trace of ammonia (waste product)
Controlled by sympathetic nerves

35. 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 oil-gland ducts

36. 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

37. 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

38. 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

39. 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

40. 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
(system’s
output)
Response to the stimulus leads to change.
Change is “fed back” to the receptor.

41. Negative Feedback
Some activity alters a condition in the internal environment
Alteration triggers a response
Response reverses the altered condition

42. Positive Feedback Some activity alters the internal environment
The alteration triggers a response
The response intensifies the change in the internal condition