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, CO 2 products, electrolytes and proteins. BLOOD 55% 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