Unit 2 - Anatomical Organization, Histology, and Maintenance of Homeostasis

Cellular Organization

cell —> tissue —> organ —> organ system

cells

basic unit structure/function

tissues

group of specialized cells which perform a specific function

merocrine

• cells secrete their substances by exocytosis

• salivary and sudoriferous (sweat) gland

apocrine

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

• mammary and ceruminous (ear) glands

holocrine

• the entire cell disintegrates to excrete its substance

• sebaceous (oil) glands

extracellular matrix

material found in space between tissue cells, contains ground substance and fibers, produced by connective tissue cells that are embedded within it. composed of ground substance + protein fibers.

types of extracellular matrix

ground substance and 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, located in bones, cartilage, tendons, ligaments, and skin

elastic fibers

it stretches and recoils elastic protein; located in skin, blood vessels, and lung tissue

reticular fibers

supports and strengthens, collagen protein with glycoprotein coating; forms supporting framework for many soft organs

cartilage

chondroblasts, secretes gelatinous matrix

bone

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

Mature Resident Cells

mature fibroblasts, blood cells, mast cells, adipocytes, osteocytes, chondrocytes, macrophages

mature fibroblasts

secrete fibers and 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), platelets/thrombocytes (blood clotting)

mast cells

produce histamine, a chemical that triggers inflammatory response which increases vascular permeability (swelling) and attracts more phagocytic cells to the site.

adipocytes

fat cells/store triglycerides, found below skin and around organs

osteocytes

mature bone cells

chondrocytes

mature cartilage cells

macrophages

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

muscle tissue

skeletal, cardiac, and smooth; contract to produce voluntary or involuntary movements.

nervous tissue

initiates and transmits nerve impulses to coordinate activities of the body

two major types of cells

neurons and neuroglia

neurons

specialized to transmit electrical (nerve) impulses; sense stimuli —> convert stimuli into nerve impulses —> signal other nerves, muscles, or glands to respond

neuroglia 

do not generate or conduct nerve impulses, smaller than neurons, many times more numerou

astrocytes (CNS)

help provide proper environment for the generation of nerve impulses, provide nutrients to neurons, take up excess neurotransmitters, maintain proper ion balance (Ca 2+ and K+)

microglial cells (CNS)

engulf invading microbes, clear debris of dead cells

obligodendrocytes (CNS)

provide support for surrounding neurons, produce myelin sheaths around adjacent neuron axons

ependymal (CNS)

line cavities of the brain filled with CSF, forms CSF and aids with its circulation

schwann cell (PNS)

produce myelin sheath around axons of PNS neruons

satelite cell

from a protective layer around neuron cell body in PNS providing nutritional and metabolic support

types of neuroglia (glial cells)

astrocytes, microglial cells, obligodendrocytes, ependymal, schwann cells, satellite cells

organ

two or more tissues, work together to perform a specific function

organ system

a group of related organs that have a common function

regulation

sum of all the processes that are occuring in the body to maintain homestasis

maintenance of homeostasis

maintenance of a stable internal environment (optimal conditions), necessary for normal body functioning, to sustain life, homeostatic imbalance- a disturbance in homeostasis resulting in disease/breakdown

feedback mechanism

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

negative feedback

includes most homeostatic control mechanisms, shuts off the original stimulus, or reduces its intensity ex. body temperature, glucose levels

positive feedback

the response amplifies the initial stimulus, not common- only blood clotting and childbirth, non-anatomy example: alarm or panic can spread by positive feedback among a herd of animals to cause a stampede

glandular epithelium

makes up the secreting portions of exocrine glands, epithelial tissue specialized for secretion

endocrine glands

secretions enter the extracellular fluid and diffuse into the 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 the skin or into the lumen (interior space) of a hollow organ. glands include sweat and salivary glands. exocrine glands are hollow; lined by glandular epithelium

connective tissue

most abundant, used for binding and supporting, major transport tissue (blood), stored energy (adipose), does not occur on free surfaces, has rich nerve and blood supply (except cartilage), not 100% cellular

mesenchymal connective tissue

all connective tissues derive from the mesodermal layer of the embryo, first connective tissue to develop in the embryo from which all connective tissues are later derived, clusters of mesenchymal stem cells are scattered throughout adult tissue and supply the cells needed for replacement and repair after a connective tissue injury

skeletal muscle tissue

striated, voluntary, attached to bones of the skeleton, controls movements an locomotion

smooth muscle tissue

non-striated, involuntary, located in walls of hollow organs, blood vessels, intestines, urinary tract, change of diameter of blood vessels. Eliminate waste. Move materials along digestive tract.

cardiac muscle tissue

striated/intercalated discs, involuntary, walls of heart, pumps blood

epithelial tissue

• the upper (apical) surface of __ is free, or exposed to the outside of the body or to an internal body cavity. The lower (basal) surface rests on connective tissue.

• basement membrane forms between the epithelial and connective tissue

• densely packed; little extracellular space between adjacent cells

• avascular; lacks 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