An organ performs functions that none of its component tissues could carry out alone.
These functions emerge from the coordinated efforts of tissues.
Coordinated interactions is a basic feature at all levels in an animal’s structural hierarchy.
20.8 Organs are made up of tissues
20.10 Organ systems work together to perform life’s functions
Each organ system
typically consists of many organs,
has one or more functions, and
works with other organ systems to create a functional organism.
Figure 20.10_L Blood vessels Heart Circulatory system Respiratory system Nasal cavity Pharynx Larynx Trachea Bronchus Lung Bone Cartilage Skeletal system Muscular system Skeletal muscles Integumentary system Hair Skin Nails Urinary system Digestive system Urinary bladder Small intestine Large intestine Kidney Ureter Urethra Mouth Esophagus Liver Stomach Anus
Figure 20.10_R Endocrine system Thymus Adrenal gland Pancreas Testis (male) Hypothalamus Pituitary gland Thyroid gland Parathyroid gland Ovary (female) Lymphatic and immune systems Lymph nodes Appendix Bone marrow Thymus Spleen Lymphatic vessels Reproductive system Female Oviduct Ovary Uterus Vagina Male Seminal vesicles Prostate gland Vas deferens Penis Urethra Testis Nervous system Brain Sense organ (ear) Spinal cord Nerves
20.13 Structural adaptations enhance exchange between animals and their environment
Animals cannot survive unless they can exchange materials with their environment, and this exchange must extend to the cellular level.
Oxygen and nutrients must enter the cell, and carbon dioxide and other metabolic wastes must exit.
Only molecules dissolved in water can move across the plasma membrane.
Every organism is an open system that must exchange matter and energy with its surroundings.
Cells in small and flat animals can exchange materials directly with the environment.
Organisms exhibit a variety of modifications, both physiological and anatomical, to compensate for changes in the surface area to volume ratio associated with size differences. One example of this is the higher metabolic rates found in smaller animals. Because of their large surface area relative to volume, small animals lose heat at much higher rates than large animals , and therefore must produce more heat to offset the effects of thermal conductance. Another example is the variety of internal transport systems that have developed in plants and animals for actively moving materials throughout the organism, thus enabling them to circumvent the limits imposed by passive diffusion. Many organisms have developed structures that actually increase their surface area: the leaves on trees, the microvilli on the lining of the small intestine, root hairs and capillaries, and the convoluted walls of arteries, to name but a few.
Larger, complex animals have less surface area relative to volume
Rely on specialized surfaces for exchanging materials with the environment
Interstitial fluid ( 組織液 ) provides for indirect exchange between blood and body cells.
Branching and folding increase surface area of the lungs, intestines, and kidneys.
Circulatory systems modification in large animals due to the physical limitation caused by surface-to-volume ratio.
The respiratory system exchanges gases between the external environment and blood.
The digestive system acquires food and eliminates wastes.
The excretory system eliminates metabolic waste.
The circulatory system
distributes gases, nutrients, and wastes throughout the body and
exchanges materials between blood and body cells through the interstitial fluid that bathes body cells.
External environment Mouth Food CO 2 O 2 Animal Respiratory system Digestive system Circulatory system Nutrients Interstitial fluid Body cells Excretory system Intestine Anus Unabsorbed matter (feces) Metabolic waste products (urine) Heart Blood
20.14 Animals regulate their internal environment
100 years ago, French physiologist Claude Bernard recognized that two environments are important to animal:
The internal environment of a vertebrate is the interstitial fluid that fills the space around the cell.
External environment Internal environment Small fluctuations Large fluctuations Homeostatic mechanisms Homeostasis ( 恆定性 ) the active maintenance of a steady state within the body. An interplay between outside forces that tend to change the internal environment and the internal control mechanisms that oppose such changes.
20.15 Homeostasis depends on negative feedback
What is negative feedback?
Proportional control makes fluctuations smaller
Proportional control ( 比例式控制 ). The action taken, the feedback, is in proportion to the degree the system diverges from the ideal point.
Thermostat in brain activates cooling mechanisms Temperature rises above normal Temperature increases Blood vessels in skin dilate and heat escapes Thermostat shuts off warming mechanisms Homeostasis: Internal body temperature of approximately 36 − 38 C Thermostat shuts off cooling mechanisms Blood vessels in skin constrict, minimizing heat loss Skeletal muscles rapidly contract, causing shivering, which generates heat Sweat glands secrete sweat that evaporates, cooling body Temperature decreases Temperature falls below normal Thermostat in brain activates warming mechanisms