Animal Tissues and Structures

• Blood vessels are a system of tubes including arteries (carry blood away), veins (towards), and capillaries (link arteries and veins), and are major for the circulatory system.
• The dermis is a connective tissue layer beneath the epidermis containing epithelial, muscle, and nervous tissue, arterioles, venules, lymph vessels, hair follicles, and glands.
• Stratified epithelium is tissue with 2+ layers covering internal/external surfaces, found in the esophagus, skin, and body openings (mouth/anus), that can withstand wear and tear.
• Glial cells surround, support, insulate, and protect neurons, and crucially regulate the interstitial fluid.
• Connective tissue supports, strengthens, and binds tissues/cells, with a large amount of extracellular matrix; main categories = loose, dense, and specialized.
• Basement membrane is a thin, noncellular layer of fibrous proteins that supports and anchors epithelial membranes.
• Lymph nodes are small swellings that filter lymph (interstitial fluid) past white blood cells; the human body has ~500 lymph nodes.
• Bone marrow is tissue inside bone cavities and its cell-based components originate from cells in the bone marrow.
• Thrombin is an active enzyme that cleaves fibrinogen, starting a series of reactions that form insoluble fibrin strands.
• Fish hearts have two main contractile chambers; fish bodies are supported by water, so hearts don't need to pump against gravity and blood pressure is lower than terrestrial vertebrates.
• Fish evolved into amphibians.
• Cellular respiration creates CO2 as waste; CO2 diffuses from cells into the blood, is carried to skin capillaries, and diffuses out.
• Gills are respiratory structures in aquatic animals, with thin projections increasing surface area and dense capillary profusion that carry blood close to the gill surface aiding gas exchange.
• Most fish have an operculum as a bony flap that protects their gills.
• Countercurrent exchange evolved in fish to maximize oxygen uptake from water by flowing water over the gills in the opposite direction of blood flow.
• Vertebrate lungs are chambers with moist respiratory surfaces protected in the body; the first vertebrate lung was in a freshwater fish and was an outpocketing of the digestive tract.
• Surface area is the total area of the outer surface of a cell, tissue, organ, or organism where interactions with the environment occur.
• Flatworms have a gastrovascular cavity and gas exchange occurs through their gas-permeable skin surface; Their flattened shape ensures cells are close to the skin.
• The large intestine is ~2.5 inches wide and 5 feet long (wider but shorter than the small intestine); most of the large intestine is the colon, and ~6 inches is the rectum.
• The leftovers of digestion/absorption from the small intestine flow into the large intestine, home to a flourishing bacteria population and producer of feces, while hosting an extensive bacterial ecosystem.
• The small intestine is a long, muscular tube that receives chyme, completes chemical digestion, and absorbs nutrients. It comprises the duodenum, jejunum, and ileum and is where most absorption occurs.
• A gastrovascular cavity is a cnidarian digestive chamber with a single opening used for both ingesting food and ejecting waste.
• The cnidarian uses stinging tentacles to capture animals.
• Sand provides a habitat for microbes, worms, crustaceans, and animals and contains microorganisms (bacteria/fungi) crucial in nutrient cycling and decomposition.
• Cellulose is the major structural component of plant cell walls, and the most abundant carbohydrate on the planet, however few organisms can digest it.
• Synthesized fats are concentrated energy sources with 2x the calories of carbs/proteins, and are hydrophobic, storing energy, providing insulation, and is often stored beneath the skin.
• Urine is a watery fluid containing removed substances that get excreted to maintain homeostasis.
• Kidneys filter blood, are fist-sized organs at waist level, with the renal cortex as the outermost layer.
• Your blood volume passes through the kidneys ~60x daily and each kidney contains ~1 million nephrons.
• ADH (antidiuretic hormone) controls aquaporin numbers and is secreted by the pituitary gland. and causes cells of the distal tubule and collecting duct to insert aquaporin proteins; absence of ADH makes membranes nearly impermeable to water.
• ADH levels control blood osmolarity by managing water levels in urine.
• A venule is a microcirculation vein that allows blood to return from the capillary beds and drain into the venous system.
• Filtrate is passed through a filter from the renal-corpuscle, containing water, ions, and waste products that get separated from the blood.
• Nephridia are tubular structures in some invertebrates' urinary systems (earthworms/mollusks) within the coelom, beginning with funnel-like openings.
• Malpighian tubules are primary excretory/osmoregulatory organs found in insects/arthropods that remove waste and maintain osmotic balance.
• They absorb solutes, water, and wastes from hemolymph, and release them as solid nitrogenous compounds.
• Urea is converted into its less toxic version.
• Most terrestrial vertebrates generate ammonia in their livers to create urea, while marine sharks/rays produce, excrete, and store concentrated urea.
• Cancer is the uncontrolled replication of the body’s cells that causes disease and can be triggered various ways; the immune system usually destroys cancer cells if they are present.
• Viruses are microscopic infectious microbes which replicate inside cells and infect all life forms, and are found in almost every ecosystem on Earth.
• HIV (human immunodeficiency virus) causes AIDS by infecting and destroying helper T cells and undermines the immune system.
• HIV hijacks the T cell's machinery forcing it to make more viruses, and is transmitted by direct contact with infected person’s skin, mucous membranes, or virus-laden body fluids (blood, semen, vaginal secretions, breast milk).
• HIV infection can be spread by sexual activity, sharing needles, and blood transfusions.
• A woman infected with HIV can transmit the virus to her child during pregnancy, childbirth, or breast-feeding
• Antibodies are proteins made by B cells to recognize and destroy invading microbes, are Y-shaped proteins, comprising a pair of identical large chains and a pair of identical small chains, and include 5 categories.
• IgM and IgD antibodies attach to the surfaces of B cells: when an IgM or IgD antibody on the surface of a B cell binds an antigen, this triggers multiplication of the B cell
• IgG antibodies are most commonly found in blood/lymph/interstitial fluid, destroy invading microbes, cross the placenta, and defend the developing fetus against disease.
• IgA antibodies are secreted onto digestive/respiratory tract surfaces, also into saliva/breast milk, where they combat invaders entering via the mouth and nasal passages, and provide temporary defenses for nursing infants
• IgE antibodies are responsible for allergic reactions
• White blood cells fight infection: some engulf foreign particles/destroy infected cells, while chemicals released by damaged cells/proteins released by white blood cells trigger inflammation and fever.
• The nonspecific response is a generalized response to pathogen infections, involves white blood cells/plasma proteins, and is innate immunity, made up of phagocytes and barriers.
• Histamine relaxes smooth muscle surrounding arterioles, increasing blood flow, and makes capillary walls leaky, accounting for redness, warmth, and swelling as an inflammatory response.
• Oxytocin causes contractions of the uterus' muscles during childbirth, the milk let-down reflex in nursing mothers, stimulating muscle tissue within mammary glands of breasts to contract.
• Oxytocin acts directly in the brain, causing behavior changes.
• Paramecium are eukaryotic, unicellular ciliates, widespread in freshwater, brackish, and marine environments, using cilia to move and gather food (bacteria/microorganisms), and reproduce both asexually and sexually.
• Hormones are chemicals produced in small quantities, transported in the bloodstream, and regulate other cells.

Types of hormones

• Local Hormones diffuse through the interstitial fluid and affect nearby cells, and are produced by small glands, clusters of cells, or even single cells.
• Steroid hormones are synthesized from cholesterol.
• Peptide Hormones comprise chains of amino acids.
• Amino Acid Derived Hormones are composed of one or two modified amino acids.
• GABA (gamma-aminobutyric acid) is the primary inhibitory neurotransmitter in the central nervous system and plays a crucial role in calming brain activity/regulating physiological functions (anxiety, stress, sleep).
• GABA’s primary function is to reduce neuronal excitability by inhibiting nerve transmission.
• Neurotransmitters are chemicals that function as messengers in synaptic communication and are released at synapses.
• The limbic system is a diverse group of foreign structures in a ring between the thalamus and cerebral cortex, including the hippocampus, hypothalamus, and amygdala, as well as nearby regions of the cerebral cortex.
• This system helps to generate emotions like fear, rage, and sexual desire. including the hippocampus, hypothalamus, and amygdala, as well as nearby regions of the cerebral cortex.
• Hippocampi are paired structures in the cerebrum that are crucial for the formation of long term memory, are particularly important for “place learning” in most/all vertebrates.
• The Medulla is part of the hindbrain that resembles an enlarged extension of the spinal cord, controlling automatic functions such as breathing, heart rate, blood pressure and swallowing.