unit 2: cellular organization, histology, and homeostasis

simplest to complex level of organization

cells —> tissues —> organ —> organ system

cells

basic unit structure/function

tissues

group of specialized cells which perform a specific function

4 types: epithelial, connective, muscular, nervous

epithelial tissue (lining & covering)

• upper (apical) surface of epithelium is free/exposed to outside of body/internal body cavity

• lower (basal) surface rests on connective tissue

• basement membrane - forms between epithelial + connective tissues

• densely packed; little extracellular space between adjacent cells

• avascular - lacks its own blood supply; nutrients diffuse from neighboring connective tissue very high rate of mitosis; renews/repairs itself rapidly

• protection, filtration, secretion, absorption, excretion

epithelial tissue (shape)

1. squamous (flattened)

2. cuboidal

3. columnar

epithelial tissue (# layers)

1. simple (1 layer)

2. stratified (many layers)

3. pseudostratified (appears layered, but nuclei does not line up)

endocrine glands

• secretions enter extracellular fluid and diffuse into bloodstream

• no ducts, secretions are called hormones

• glands include adrenal, thyroid, and pituitary

exocrine glands

• secrete products into a duct that leads to the surface of skin/into lumen (interior space) of a hollow organ

• glands include sweat, salivary glands

• glands are hollow; lined by glandular epithelium

glandular epithelium

makes up secreting portions of exocrine and endocrine glands

merocrine glands

cells secrete their substances by exocytosis

apocrine glands

a portion of the cell membrane that contains the secretion buds off

holocrine glands

entire cell disintegrates to excrete its substance

connective tissue

• most abundant tissue

• supports/strengthens/protects/insulates

• major transport tissue (blood)

• stored energy (adipose)

• doesn’t occur on free surfaces

• has rich nerve + blood supply (except cartilage)

mesenchymal connective tissue

• all connective tissues derive from mesodermal layer of embryo

• 1st connective tissue develops in embryo from which all connective tissues are later derived

• clusters of mesenchymal stem cells are scattered throughout adult tissue + supply cells needed for replacement and repair after a connective tissue injury

extracellular matrix

• material found in space between tissue cells

• contains ground substance and fibers; produced by the connective tissue cells that are embedded within it

• composed of ground substance + protein fibers

ground substance

can be fluid/semi-fluid/gelatinous/calcified

protein fibers

collagen fibers, elastic fibers, reticular fibers

collagen fibers

very strong and flexible; contain collagen protein

elastic fibers

stretch and recoil; elastin protein

reticular fibers

support + strength; collagen protein w/ glycoprotein coating

merocrine glands location

salivary and sudoriferous (sweat) glands

apocrine glands location

mammary and ceruminous glands

holocrine glands location

sebaceous (oil) glands

collagen fibers location

bones, cartilage, tendons, ligaments, skin

elastic fibers location

skin, blood vessels, lung tissue

reticular fibers

forms supporting framework for many soft organs; ex. the spleen

immature class of “blast” cells

“blast” cells secrete the matrix and produce new cells

loose/dense connective tissue

cartilage: chondroblasts secrete gelatinous matrix

bone: osteoblasts; bone formation, secretion of organic fibers and inorganic salts to create crystalline matrix

• may differentiate into mature cells

mature fibroblasts

secrete fibers + ground substance of matrix in loose and dense connective tissue, lots of collagen

blood cells

• red blood cells/erythrocytes - transport oxygen

• white blood cells/leukocytes - immune response

  • ex. plasma cells - secrete antibodies/immune system

• platelets/thrombocytes - blood clotting

mast cells

produce histamine: chemical that triggers inflammatory response which inc vascular permeability (swelling) and attracts more phagocytic cells to the site

adipocytes

fat cells/store triglycerides (found below skin + around organs)

osteocytes

mature bone cells

chondrocytes

mature cartilage cells

macrophages

develop from WBC’s; move abt in connective tissue as scavengers clearing foreign particles

skeletal muscle tissue

• striated, voluntary

• location: attached to bones of the skeleton

• function: movements + locomotion

smooth muscle tissue

• non-striated, involuntary

• located in walls of hollow organs; blood vessels, intestines, urinary tract

• function: change diameter of blood vessels, eliminate waste, move materials along digestive tract

cardiac muscle tissue

• striated/intercalated discs, involuntary

• location: walls of heart

• function: pump blood

nervous tissue

initiates + transmits nerve impulses to coordinate activities of the body

neurons

• specialized to transmit electrical (nerve) impulses

• sense stimuli: convert stimuli into nerve impulses and signal other nerves, muscles, or glands to respond

neuroglia

• don’t generate or conduct nerve impulses

• smaller than neurons, many times more numerous

astrocytes

• help provide proper environment for generation of nerve impulses

• provide nutrients to neurons

• take up excess neurotransmitters

• maintain proper ion balance (CA 2+ and K+)

microglial cells

• engulf invading microbes

• clear debris of dead cells

olgiodendrocytes

• provide support for surrounding neurons

• produced myelin sheaths around adjacent neuron axons

ependymal

• line cavities of brain filled w/ CSF

• forms CSF and aids w/ its circulation

schwann cell

produce myelin sheaths around axons of PNS neurons

satellite cell

form a protective layer around neuron cell bodies in PNDS providing nutritional and metabolic support

organs

2 or more tissues, working tg to perform a specific function

ex. stomach, lungs, liver, pancreas, trachea

organ system

a group of related organs that have a common function

integumentary system

skin and structures derive from it such as hair, nails, and sweat + oil glands

skeletal system

all the bones + joints of the body and their associated cartilages, includes teeth

muscular system

specifically skeletal muscle tissue, other muscle tissue includes cardiac + smooth

cardiovascular/circulatory system

blood, heart, and blood vessels

lymphatic/immune system

lymph, lymphatic vessels, and structures containing lymphatic tissue such as spleen, thymus, tonsils

nervous system

brain, spinal cord, nerves, and sense organs

endocrine system

hormone producing glands such as pituitary, thyroid, and pancreas

respiratory system

lungs and airways leading into and out of them

digestive system

organs of gastrointestinal tract (mouth, esophagus, stomach, intestines) and accessory organs (salivary, glands, pancreas, liver and gallbladder)

urinary system

kidneys, ureter, urinary bladder, urethra

reproductive system

gonads (testes/ovaries)

integumentary system function

• regulates body temp

• eliminates some wastes

• detects sensations

• protects

skeletal system function

• supports + protects body

• assists in mvt

• produces blood cells

• stores minerals + lipids

muscular system function

• powers mvts of the body

• stabilizes body position

• generates heat

cardiovascular/circulatory system function

• pumped blood carries oxygen/nutrients to cells + carbon dioxide/wastes away from cells

• helps regulate pH, temp + water content of body fluids

• helps defend against disease + mend damaged blood vessels

lymphatic/immune system function

• returns proteins + plasma to the cardiovascular system

• site of maturation/proliferation of certain types of White Blood Cell’s

• production of antibodies to combat disease

• transport of fats from gastrointestinal tract to the cardiovascular system

nervous system function

• regulates body activities in response to internal + external stimuli

• interprets stimuli + responds thru muscular contractions/glandular secretions

endocrine system function

regulates body activities thru hormones, chemicals transported in the blood to target cells

respiratory system function

• transfers oxygen from inhaled air to blood and carbon dioxide from blood to exhaled air

• helps regulate pH balance of body fluids

digestive system function

physical + chemical breakdown of foods, absorbs nutrients, eliminates solid wastes

urinary system function

• regulates volume and chemical composition of blood

• eliminates metabolic wastes

• regulates fluid and electrolyte balance

• helps maintain pH of body fluids + calcium balance of the body

• secretes hormones that regulate red blood cells production

reproductive

• produce gametes and release hormones that regulate reproduction

• transport + store gametes

maintenance of homeostasis regulation

• maintenance of a stable internal environment (optimal conditions)

• necessary for normal body functioning, to sustain life

• homeostatic imbalance - a disturbance in homeostatic resulting in disease/breakdown

feedback mechanisms

mechanisms by which body senses + responds to internal and/or external stimuli in order to maintain homeostasis

negative feedback

wants to reverse/negate stimulus

• includes most homeostatic control mechanisms

• ex. body temp, glucose levels

• shuts off og stimulus/reduces its intensity

positive feedback

• reponse amplifies the initial stimulus

• not common - only blood clotting and childbirth

• non-anatomy ex: alarm/panic can spread by positive feedback among a herd of animals to cause a stampede