ANS 123 Lecture 1-6 QUIZ 1

Development

Cellular changes over time that enable tissues and subsequently organs to take on different and increasingly more complex roles & functions

Process through which a single, totipotent cell (e.g., fertilized egg) gains complexity to become a complete organism

• Increasing complexity ⇄ Decrease in number/range of genes being expressed ⇄ Loss of potency[expression]

Growth

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

Accretion

Gradual accumulation/buildup through adhesion of external parts & particles

“-blast”:

To sprout

o Used to indicate an immature cell that can undergo mitosis and retains potency

• The prefix indicates the cell lineage of the immature cell

Ex. Chondroblast

= Immature cartilage cell

“-clast”:

To destroy

o Used to indicate a differentiated cell that destroys tissue

• The prefix indicates what type of tissue

Ex. Osteoclast

= Bone destroying cell

“-cyte”:

Cell

o Used to refer to a mature, completely differentiated cell

Ex. Myocyte

= Mature muscle cell

Fertilization

Fusion of sperm & egg

Cytokinesis

Cell division

Cell determination

When an immature cell “shuts down” gene expression of portions of its genome and reduces its cellular potency to become a more specialized cell type

o Still cannot function as the specialized cell type

Cell differentiation

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

o Genes that express products for that specific function get “switched on”

o Results in cellular diversity

Apoptosis

Programmed cell death

o Critical process throughout a living organism’s lifetime

Hypertrophy

Growth that occurs when cells increase in size

Hyperplasia

Growth that occurs when cells increase in number

o Can occur in combination or separately

Average daily gain

Typically measured in mass (e.g., pounds/ kilograms)

o Generic measure that includes fat, muscle, and bone

What types of tissues are there?

• Nervous

• Epithelial

• Muscle

• Connective

What are tissues?

Aggregate of cells of a particular kind + Intercellular substance (i.e., “cellular packaging”)

• Act synergistically [come together and work together] to fulfill specific function

• Intercellular substance typically made up of/produced by connective tissue cells

Ex. Muscle tissue

• Aggregate of muscle tissue cells + Connective tissue sheaths

• Responsible for movement

Nervous Tissues: Brain, Spinal Cord, Nerves

• Aggregate of:

1. Neurons/Nerve cells

2. Neuroglia/Glial cells

• Responsible for coordinating the various functions of the body

Nervous tissue: 1. Neurons/Nerve cells

Communicate/carry messages throughout the body using electrical pulse

Nervous tissue: 2. Neuroglia/Glial cells

• Support, bind, & defend nervous tissue cells

o Insulation

o Structure

Nervous system

Collection of nervous tissue that interact

1. Central nervous system (CNS) – Consists of brain and spinal cord

2. Peripheral nervous system (PNS) – Consists of bundles of nervous

1. Central nervous system (CNS) – Consists of brain and spinal cord

Integrates and coordinates all bodily functions

2. Peripheral nervous system (PNS) – Consists of bundles of nervous

o Sensory component: Detects stimuli (both internal & external) and delivers information to CNS→ receive info through neurons

o Motor component: Carries response messages from CNS to appropriate tissues throughout body→ have info effect something via motor system

Soma

Body of the neuron

o Contains nucleus + other typical cell organelles (mitochondria)

Processes

Extensions from soma

o Dendrites: Receive signals from other neurons/cells & carry TO soma

o Axons: Carry signals FROM soma & transmit to other neurons/cells

Multipolar Neuron [Most common]

Description: Multiple dendrites from soma in opposite direction of axon

Location: Brain and spinal cord (e.g., CNS)

Function: Integrates information from multiple inputs

Pseudo-unipolar Neuron: Pseudo” because axon branches split from a single one

Description: Single axon split into 2 branches; each branch goes in different direction

Location: Throughout body, closely associated with spinal cord

Function: Receives sensory information & transmits to spinal cord

Bipolar Neuron

Description: Single dendrite extends from soma in opposite direction of axon

Location: Eye (e.g., retina), nose (e.g., olfactory tissue), and ear (e.g., vestibular-cochlear nerve)

Function: Receives highly specialized signals & transmits to nerve bundles that link to the brain

• Plays crucial role during neurogenesis

Glial cells: Supporting cells

• Constitute ~ ½ total mass of nervous tissue

• Do not participate in electrical signaling

CNS: Oligodendrocytes, Astrocytes, microglia, Ependymal Cells

PNS: Schwann cell, Satellite cells

Glial Cells: Oligodendrocytes

Central Nervous System

Produce myelin sheaths that wrap around some axons; gives white appearance; single cell → multiple sheaths

Glial Cells: Astrocytes

Central Nervous System

Control levels of neuro- transmitters & ions at synapses; participate in blood-brain barrier

Glial Cells: Microglia

Central Nervous System

Immune cells of nervous tissue - behave as macrophages

Glial Cells: Ependymal Cells

Central Nervous System

Line Ventricles & produce cerebral-spinal fluid [aqueous cushion for protecting brain]; participate in blood-brain barrier

Glial Cells: Schwann Cells

Peripheral Nervous System

Produce myelin sheaths around some axons; single cell → single sheath

[NOTE: Text considers these to be specialized oligodendrocytes]

Glial Cells: Satellite Cells

Peripheral Nervous System

Control levels of neuro- transmitters & ions at synapses

[NOTE: Same term used for cells in muscle tissue]

Epithelial Tissues: Lining of GI tract organs and other hollow organs, Skin surface [epidermis]

Cover exposed surfaces of body

o Protect underlying tissue from its environment (both internal and external)

Control nutrient flow to underlying tissues

House secretory cells

Aid in sensory communication

Ex. Cells in taste buds, retinas, and nasal cavity linings

Typically associated with basal lamina/basement membrane

o Basal lamina/Basement membrane : Attaches & anchors epithelial cells to underlying tissue

• Extracellular, connective tissue matrix

Integument: Largest organ = Skin

Composite membrane

o Epithelial tissue = Epidermis

• Appendages: Hair follicles, sebaceous & sweat glands, hooves/nails, horns

o Connective tissue = Dermis (houses secretory cells)

• (Hypodermis: Not part of integument – anchors integument to rest of body)

Integument: Associated with commercially important products

o Wool/hair

o Feathers

o Leather

• Also produces: Hooves/nails, Horns

Muscle Tissue: Cardiac Muscle, Smooth Muscle, Skeletal muscle

1. Enables movement: Muscle cells contract & relax

2. Participates in thermoregulation: Contracting muscle cells generate heat

• 30-40% of total body mass: Major drain on energy efficiency

Muscle cells→ Muscle fiber, myocyte, myofiber, muscle cell

Unique characteristic: Physiological & Functional plasticity ⇒ Retain ability to change physiology and thus, function throughout life

o Embryonic, fetal/perinatal, α-cardiac, Types 1, 2A, 2B, 2X*

Sarcolemma

Muscle fiber cell membrane

o Responsive to electrical stimulation[ion changes] by motor neurons

o Multiple pores enable communication throughout cell

Sarcoplasm

Muscle fiber cytoplasm

o High concentrations of proteins & mitochondria

o Sarcoplasmic reticulum: Muscle fiber endoplasmic reticulum

• Repositories of Ca2+: controls calcium/release or suck back to reticulum

Cytoskeletal elements

o Actin filaments (microfilaments)

o Myosin

Types of Muscle Tissue

1. Smooth

2. Cardiac

3. Skeletal*

Muscle tissue: Characterized based on:

Function

Cell structure

• Shape

• # of nuclei

• Presence or absence of striations: Organization of striations, if present

Contractions

• Type - Voluntary or Involuntary

• speed, direction, coordination

Smooth muscle

Function: Move substances within body: Surrounds many internal organs & vessels of circulatory system

Cell structure

o Shape: Spindle

o Nuclei #: 1/cell

o Striations?: No

Contractions

o Type: Involuntary

o Speed: Slow

o Direction: Multi-directional

o Coordination: Loose

Cardiac muscle

Function: Rhythmic contractions of heart; creates tight jxns, more opportunities to grab each other

Cell structure

o Shape: Short & branched

• Interdigitated: branching allows this, intercalated disks allow end to end of fiber holding

o Nuclei #: 1-2/cell

o Striations?: Yes

Contractions

o Type: Involuntary

o Speed: Fast & slow

o Direction: Unidirectional

o Coordination: High

Skeletal muscle

Function: Movement of body; Attached to bones in skeleton

Cell structure

o Shape: Elongated & cylindrical

o Nuclei #: Multi-nucleated (hundreds/cell)/ Actual # directly proportional to length

o Striations?: Yes/ Aligned

Contractions

o Type: Voluntary

o Speed: Fast & slow

o Direction: Unidirectional

o Coordination: High

Connective Tissue: Fat and other soft padding tissue, Bone, Tendon

Cells

1. Fixed: Produce ground substance & proteins that are turned into fibers

• Specific to each connective tissue type

2. Wandering

Protein fibers: At least one type found in all categories of connective tissue

1. Collagen

2. Reticular

3. Elastic

Ground substance

1. Chondroitin sulfates

2. Hyaluronic acid

Extracellular Matrix:

Protein fibers: At least one type found in all categories of connective tissue

Ground substance:

1. Chondroitin sulfates

2. Hyaluronic acid

Connective tissue Fxns

• Provides structure to body

• Supports body

• Most diverse tissue type: Function dictates structure

3 main categories

1. Proper

2. Supportive

3. Specialized

Specific types of connective tissue: Proper

A. Loose/Areolar

B. Dense

i. Regular

ii. Irregular (not pictured)

Specific types of connective tissue: Supportive

A. Cartilage

i. Hyaline

ii. Elastic

iii. Fibrocartilage

B. Bone

Specific types of connective tissue: Specialized

A. Adipose

B. Blood

Connective Cells Fixed: Produce ECM (fibers + ground substance)

Proper = Fibroblasts

Supportive

o Cartilage = Chondrocytes

o Bone = Osteocytes

Specialized

o Adipose = Fibroblasts + Adipocytes

Connective Cells Wandering: Defend & clean

• Proper, Supportive & Specialized = Macrophages & Mast cells

• Specialized only: Blood & Lymph = Erythrocytes, Lymphocytes, Platelets

Connective tissue fibers: Collagen

o Protein: Fibrillar collagen

o Structure & support, esp in skin & muscles

Connective tissue fibers: Reticular

Protein: Collagen III

o Support within organs, glands, etc., and/or fine structural support

Connective tissue fibers: Elastic

o Protein: Elastin

o Stretchiness

Fibroblasts (Proper)

Mostly fibers; some ground substance

• Fibers:

o Collagen

o Reticular

o Elastic

Chondrocytes (Supportive)

Cartilage fibers

Hyaline, Fibrous, Elastic

Contained in small chambers (e.g., lacunae [grows that way/holding space) in extracellular matrix

Cartilage fibers: Hyaline

Collagen fibers; slightly more ground substance firm/rubbery

Cartilage fibers: Fibrous

Collagen fibers; little ground substance

Less Squishy

Cartilage fibers: Elastic

Mostly elastic fibers + some collagen fibers; more ground substance

Stretchy

Osteocytes (Supportive)

Bone fibers

o Collagen fibers; calcium-rich ground substance [hard as cement]

Contained in lacunae

• all supportive cells are in lacunae [space in substance]

Adipocytes (Specialized)→ Fat cells

Triglyceride storage

• Mostly storage; very little ground substance

Wandering cells

Proper, Supportive & Specialized

o Macrophages: Seek out & destroy foreign bodies & damaged cells

o Mast cells: Release histamine

Specialized only

o Erythrocytes: Transport O 2 & CO 2

o Lymphocytes: Immune response

o Platelets: Clotting

EARLY development

Cellular changes over time that enable tissues and subsequently organs to take on different and increasingly more complex roles & functions

• Process through which a single, totipotent cell (e.g., fertilized egg) gains complexity to become a complete organism

Karyogamy

Fusion of ovum & sperm pro-nuclei

Germ layers

Ectoderm, Mesoderm, Endoderm

o Form the embryo

“Natal”/“Birth” and “Hatch” will often be used inter-changeably

Pre-natal: Before birth

• Peri-natal: Around birth

• Post-natal: After birth

• Neo-natal: Newly born

Cellular/Cell potency

How much of the organism’s genome a cell can express

• Stem cells

1. Totipotency

2. Pluripotency

3. Multipotency

4. Unipotency

Totipotency

ability to express ALL the genes in the organism’s genome

• Differentiate into ANY type of cell; both embryonic AND extraembryonic

Pluripotency

Ability to express genes that code for all germ layers (e.g., endoderm, mesoderm, & ectoderm)

Multipotency [Progenitor Cells]

ability to express genes that code for closely-related family of cells

• one type of layer

Delamination

Splitting single sheet of cells through loss of adhesion

Ex. Hypoblast formation

Ingression

Division & migration of cells into internal area to form a separate layer

Ex. Internal cell mass & trophoblast separation

Invagination

Depression in cell layer deepens due to cell division – sides of depression come together and pinch off from existing layer

Ex. Neural tube formation

Epiboly

Increase in # of cells on outer surface

Ex. Primitive streak formation

Involution

Inward rolling of cells along an existing membrane to create layers

Ex. Myelin sheath formation

Morphogenesis

Generation, differentiation & growth of tissues & organs during development (i.e., morphology)

General term that covers

o Cleavage, Layer formation, Gastrulation, Neurulation, Organogenesis, Etc.

• Commences post-fertilization

Morphogenesis: Associated with increasing cellular complexity and loss of cellular potency

During early development achieved by creating 3 “new” germ layers

⇒Loss of totipotency

Obvious differences: The ovum→ Birds

Yolk→ Marcolecithal [large]

Yolk distribution→ Telolecithal [non-uniform]

Cleave pattern→ Meroblastic [incomplete discoidal] each time cells divide, you don’t get yolk by by bit remains intact entire time

• only dividing cells divide little dish shape floating on top of yolk

Obvious differences: The ovum→ Mammals

Yolk→ Alecithal [absent]

Yolk distribution→ Isolecithal [uniform]

Cleave pattern→ holoblastic [complete], rotational → yolk involved in same division

Surprising similarities in development for avian/ungulates/rodents

At some points during development, ungulate processes are more similar to avian processes than they are to rodents.

similarities between avian and rodents

• cleavage, organogenesis, gastrulation

Cleavage: Functions

1. Increase # of cells via mitosis without growth

o Cell number ⇌ Cell size [daughter cells get smaller]↴

2. Establish embryonic vs extraembryonic cell lines

• Results in:

o Avian blastoderm

o Mammalian blastocyst

• Cleavage ends when blastocyst makes contact with uterine wall

Avian cleavage: Discoidal

Discoidal: Cleaving cells clump together into a disc- shape

Avian cleavage: Meroblastic

Cleavage plane is Incomplete; yolk remains intact

Avian cleavage: Functions: 1. Increase number of cells thru cell division

Meroblastic [incomplete] cleavage

about the same as moving through next division size of cell and # relatively same

Avian cleavage: Meroblastic 1-16 divisions

Symmetric division ONLY =

Daughter cells are identical

o BOTH daughter cells form INcomplete cell membrane = Open cell

• Cytoplasm mixes with yolk

Avian cleavage: Meroblastic After 16

Asymmetric division begins =

Daughter cells not identicAsymmetric division begins =

Daughter cells not identical!

o One forms complete (“closed”) cell membrane

= Blastomere

o One is an open cel!

o One forms complete (“closed”) cell membrane = Blastomere

o One is an open cell

Avian cleavage: Functions 2. Establish embryonic vs extra- embryonic cell lines

embryonic cell lines : form of embryo

extra-embryonic cell lines: fully defer to extra embryonic tissue

Establish embryonic vs extra- embryonic cell lines→ Blastoderm (from 64-cell stage):

Most central cells = Closed

o 5-6 cell layers thick

o Embryo only

Regions of open cells beneath & around embryo begin to form

• Mostly extra-embryonic [open daughter cells to do embryonic tissue in the periphery] ; some embr Most central cells = Closed

  o 5-6 cell layers thick

  o Embryo only

  • Regions of open cells beneath &

  around embryo begin to form

  o Mostly extra-embryonic; some

  embryo

Avian cleavage: One more function→ 3. Establish axes of polarity

o Dorsal-ventral axis [HEAD]

o Anterior-posterior axis [BUTT]

cluster of cells need direction to develop

Interaction of these axes creates a left & right side of embryo

3. Establish axes of polarity

Dorsal-ventral axis→ talking about cells that are going to become embryonic

• Dorsal = Egg shell side

• Ventral = Yolk side

Anterior-posterior axis

• More complex…[slowly rotating]

Avian cleavage: Anterior-Posterior Axis

Egg rotates 10-12 turns/hr in shell gland

• Gravity causes “heavy” blastoderm to tilt away from “top” of yolk

o Lowest end of blastoderm becomes anterior of embryo

Avian cleavage: Conclusion

The blastoderm

• Two cell lineages

1. Closed cells

2. Open cells

• Axes of polarity