ANS 123 Tissues

development

cellular changes over time that enables tissues and subsequently organs to take on different and increasingly more complex roles and functions

• increasing complexity, decrease in number/range of genes being expressed, loss of potency

growth

general and normal expansion so size through accretion of tissues similar in composition to the original tissue or organ

accretion

gradual accumulation/buildup thorugh adhesion of external parts and particles

‘-blast’

to sprout

• used to indicate an immature cell that can undergo mitosis and remain potency

ex. chondroblast=immature cartilage cell

‘-clast’

to destroy

• used to indicate a differentiated cell that destroys tissue

ex. osteoclast

‘-cyte’

cell

• used to refer to a mature, completely differentiated cell

ex. myocyte=mature muscle cell

cell determination

when an immature cell ‘shuts down’ gene expression of portions of its genome and reduced its cellular potency to become a more specialized cell type

• still cannot function as the specialized cell type

cell differentiation

precursor cell undergoes morphological changes through differential, specialized, and limited gene expression so it can perform its assigned function

• genes that express products for that specific function get ‘switched on’

• results in cellular diversity

hypertrophy

growth that occurs when cells increase in size

hyperplasia

growth that occurs when cells increase in number

average daily gain

typically measured in mass

• generic measure includes fat, muscle and bone

feed efficiency

amount of feed required to produce a given unit of animal mass

what are the 4 types of tissues

• nervous tissue

• epithelial tissue

• muscel tissue

• connective tissue

what are tissues?

aggregate of cells of a particular kind + intercellular substance (cellular packaging)

• act synergistically to fulfill specific function

ex. muscle tissue —> aggregate of muscle tissue cells + connective tissue sheaths

nervous tissue is an aggregate of

1. neurons/nerve cells

2. neuroglia/glial cells

what do neurons/nerve cells do

communicate/carry messages thoruhgout the body using electrical pulses

what do neuroglia/glial cells do

support, bind, and defend nervous tissue cells

• insulation

• structure

responsible for coordinating various functions of the body

central nervous system (CNS)

consists of brain and spinal cord

• integrates and coordinates all bodily function

peripheral nervous system (PNS)

consists of bundles of nervous tissue that emanate from CNS innervate the body

sensory component of PNS

detects stimuli both internal and external and delivers information to CNS

motor component of PNS

carries response messages from CNS to appropriate tissues throughout the body

nerve cell anatomy: soma

body of the neuron

• contains nuclues + other typical cell organelles

nerve cell anatomy: processes

extensions from soma

• dendrites: receive signals from other neurons/cells and carry to soma

• axons: carry signals from soma and transmit to other neurons

what is a multipolar neuron

multiple dendrites from soma in opposite direction of axon

• most common

where is a multipolar neuron located

brain and spinal cord (CNS)

what is the function of a multipolar neuron

integrates information from multiple outputs

what is a psuedo-unipolar neuron

• single axon split into 2 branches; each branch goes in a different direction

• psuedo—axon branches split from one

where is a psuedo-unipolar neuron located

throughout the body, closely associated with spinal cord

what is the function of a psuedo-unipolar neuron

receives sensory information and transmits to spinal cord

what is a bipolar neuron

single dendrite extends from soma in opposite direction of axon

where is a bipolar neuron found

eye (retina), nose (olfactory tissue), ear (vestibular cochlear nerve)

what is the function of a bipolar neuron

receives highly specialized signals and transmits to nerve bundles that link to the brain

• plays crucial role during neurogenesis

glial cells

constitue ~1/2 total mass of nervous tissue

• does not participate in electrical signaling

what are the glial cells in the CNS

1. oligodendrocyte

2. astrocytes

3. microglia

4. ependymal cells

what are the glial cells in teh PNS

1. schwann cells

2. satellite cells

oligodendrocyte

produce myelin sheaths that wrap around some axons; gives white appearance

• single cell—> multiple sheaths

astrocytes

control levels of neurotransmitters and ions and synapses; participate in blood brain barrier

microglia

immune cells of nervous tissue—behave as macrophages

ependymal cells

line ventricles and produce cerebral spinal fluid; participate in blood brain barrier

schwann cells

produce myeline sheaths around some axons

• single cell—> single sheath

epithelial tissue can..

cover exposed surfaces of body and protect underlying tissue from its environement

• houses secretory cells

• aid in sensory communication

• associated with basal lamina/basement membrane

integument

largest organ=skin

• composite membrane

  • epithelial tissue=epidermis

  • connective tissue=dermis

• associated with commercially important products

muscle tissue functions

1. enables movement: muscle cells relax and contract

2. participates in thermoregulation: contracting muscle cells generate heat

constitues 30-40% total body mass

unique characteristic of muscle cell

physiological and functional plasticity

• retain ability to change physiology and thus, function thorughout life

• embryonic, fetal/perinatal, alpha cardiac, types 1, 2A, 2B, 2X

3 parts of muscle cell anatomy

1. sarcolemma

2. sarcoplasm

3. cytoskeletal elements

sarcolemma

muscle fiber cell membrane

• responsive to electrical stimulation by motor neurons

• multiple pores enable communication throughout the cell

sarcoplasm

muscle fiber cytoplasm

• high concentrations of protein and mitochondria

• sarcoplasmic reticulum—muscle fiber endoplasmic reticulum, repositorites of calcium

cytoskeletal elements

actin filaments and myosin

3 types of muscle tissue

1. smooth

2. cardiac

3. skeletal

smooth muscle function

moves substances within body

• surrounds many internal organs and vessels of circulatory system

smooth muscle cell structure

shape: spindle

nuclei: 1/cell

striations: none

smooth muscle contractions

type: involuntary

speed: slow

direction: multi-directional

coordination: loose

cardiac muscle function

rhythmic contractions of heart

cardiac muscle cell structure

shape: short and branches

• interdigitated: increases surface contact between neighboring tissue and creates tight junctions

nuclei: 1-2/cell

striations: yes

cardiac muscle contractions

types: involuntary

speed: fast or slow

direction: unidirectional

coordination: high

skeletal muscle function

movement of body, attached to bones in skeleton

skeletal muscle cell structure

shape: elongated and cylindrical

nuclei: multi nucleated (hundreds/cell)

• actual # directly proportional to length

striations: yes, aligned

skeletal muscle contractions

type: voluntary

speed: fast and slow

direction: unidirectional

coordination: high

‘recipe’ for connective tissue

1. cells: fixed and wandering

2. protein fibers: collagen, reticular, elastic

3. ground substances: chondriotin sulfates, hyaluronic acid

protein fibers and ground substance comes together to form ECM

connective tissue

• provides structure to body

• most diverse type—function dictates structure

3 main categories of connective tissue

1. proper

2. supportive

3. specialized

proper connective tissue

• loose/areolar

• dense

  • regular/irregular

supportive connective tissue

• cartilage

  • hyaline

  • elastic

  • fibrocartilage

• bone

specialized connective tissue

• adipose

• blood

fixed cells: produce ECM

• proper: fibroblasts

• supportive

  • cartilage: chondrocytes

  • bone: osteocytes

• specialized

  • adipose=fibroblasts+adipocytes

wandering cells: defend and clean

• proper, supportive, and specialized

  • macrophages and mast cells

• specialized only

  • blood and lymph: erythrocytes, lymphocytes, and platelets

connective tissue fibers

• collagen

• reticular

• elastic

collagen

• protein: fibrillar collagen

• structure and support, especially in skin and muscles

reticular

• protein: collagen III

• support within organs, glands, etc, and/or fine structural support

elastic

• protein: elastin

• stretchiness

fibroblasts (fixed cells of proper connective tissue)

• mostly fibers; some ground substance

• fibers

  • collagen

  • reticular

  • elastic

• more fiber—> rigid

• more ground substance—>squishier

chondrocytes (fixed cells of supportive connective tissue)

• cartilage fibers

• contained in small pockets (lacunae) in ECM

  • prevents ECM from crushing chondrocytes

chondrocytes —3 cartilage fibers

1. hyaline: collagen fibers; slightly more ground substance

2. fibrous: collagen fibers; little ground substance

3. elastic: mostly elastic fibers and some collagen fibers; more ground substance

osteocytes (fixed cells of supportive connective tissue)

• bone fiber

  • collagen fibers; Ca+ rich ground substance

• contained in lacunae

adipocytes (fixed cells of specialized connective tissue)

triglyceride storage

• mostly storage; very little ground substance

macrophages (wandering cell for proper, supportive and specialized connective tissue)

seek out and destroy foreign bodies and damaged cells

mast cells (wandering cell for proper, supportive and specialized connective tissue)

release histamine

erythrocytes (wandering cell for specialized connective tissue)

transport O2 and CO2

lymphocytes (wandering cell for specialized connective tissue)

immune response

platelets (wandering cell for specialized connective tissue)

clotting