Tissues Study Guide

What are the 5 stages of pre-embryonic development?

Fertilization, cleavage, blastocyst stage, implantation, gastrulation

What happens in fertilization?

the paternal and maternal chromosomes fuse to form a zygote, moves down the uterine tube and goes through rounds of mitosis and cytokinesis, implants in uterine tube

What happens in cleavage?

period of rapid mitotic cell division, blastomeres are produced, relative size the same, daughter cells become smaller, solid mass of cells called a morula is made

What happens in the blastocyst stage?

morula with 32 cells has entered the uterus, blastomeres inside secrete enzymes that break down the zona pellucida, morula now becomes a blastocyst at the end of day 4, mitotic divisions continue, differentiates into trophoblast and inner cell mass

What happens in implantation?

Trophoblast cells secrete enzymes that break down the zona pellucida & allow blastocyst to hatch, blastocyst then floats free in uterine cavity until day 6, trophoblast cells adhere to the endometrium and embeds in uterine wall, trophoblast cells proliferate and form 2 layers, hCG begins to be secreted by trophoblast cells, inner cell mass undergoes change and becomes bilaminar embryonic disc

What two distinct layers are formed when trophoblast cells proliferate?

Cellular (inner) and syncytial (outer) trophoblast

What makes up the bilaminar embryonic disc?

hypoblast (deeper layer) and epiblast (superficial layer)

What day is implantation complete?

day 11

When implantation is complete, what two structures form?

amniotic sac and yolk sac

What happens in gastrulation?

changes begin and primary germ layers form, bilaminar disc elongates and broadens at anterior end and a primitive streak appears on dorsal surface, third germ cell layer develops and the bilaminar embryonic disc transforms into a three-layered embryo

What are the three layers in the three-layered embryo?

endoderm, ectoderm, mesoderm

What is a blastomere?

identical cells formed by cleavage divisions

What does a blastomere do?

secrete enzymes that break down the zona pellucida and allows the blastocyst to hatch

What is a blastocyst?

a hollow ball of cells with a cluster of cells inside known as the inner cell mass

What is a morula?

solid ball of blastomeres surrounded by zona pellucida

What are the two distinct cellular components of a blastocyst?

Trophoblast and inner cell mass

What is the function of the trophoblast?

Adheres to, digests, and implants in the endometrium, protects the conceptus from attack by the mother's immune cells

What role does the hCG play in sustaining pregnancy?

Maintains hormone production by the corpus luteum, preventing menses, helps prevent the mother's immune system from rejecting the implanted embryo

How has knowledge of the hCG hormone become clinicaly and commercially useful?

hCG in a women's blood or urine is what is detected in pregnancy tests

From what embryonic structure does the bilaminar embryonic disk originate?

Inner cell mass

What are the three primary germ layers?

endoderm, mesoderm, ectoderm

What is the endoderm?

the internal germ layer that lines the digestive, respiratory and urogenital systems and the glands associated with these systems

Which germ layer enters the primitive streak?

Endoderm

What is the mesoderm?

the middle layer between ectoderm and endoderm

What two structures are in the mesoderm?

mesenchyme and notochord

What is the notochord?

a flexible rod that provides stable support for embryo

What is the ectoderm?

outer layer at dorsal side of embryonic disc

Examples of ectoderm

structures of the nervous system and the skin epidermis

The endoderm, mesoderm, and ectoderm are all considered....

epithelia

What are the four extraembryonic membranes?

amnion, chorion, yolk sac, and allantois

What is the amnion?

a thin but tough sac of membrane that covers an embryo, surrounds the amniotic cavity

What does the amnion do?

Provides a buoyant environment that protects the developing embryo against physical trauma and helps maintain a constant temperature

Amnion is also called?

bag of waters

What is the yolk sac?

endoderm-lined membrane that receives nourishment from the endometrium, forms part of the gut

All the body organs derive from the primary germ layers. True or False?

True

The yolk sac is the source of the....

earliest blood cells

What is the allantois?

membrane sac that stores waste and is the site for gas exchange, delivers oxygen to embryo, structural base for the umbilical cord that links embryo to the placenta

What is the chorion?

outer membrane that surrounds the amnion and the embryo, develops fingerlike chorionic villi, formed by the trophoblast and the extraembryonic mesoderm

What is the function of the chorion?

helps in the exchange of nutrients, gases, and wastes between the embryo and the mother's body, protects and nurtures the embryo

What is a tissue?

groups of similar cells which are specialized to perform a specific function

What are the 4 basic types of tissue?

epithelial, connective, muscle, nervous

What does epithelial tissue do?

form boundaries between different environments, lines body cavities, forms glands, covers exposed body surfaces, forms boundaries between different environments

Example of epithelial tissue

lining of digestive tract and other hollow organs

What does connective tissue do?

supports, protects, binds other tissues together, fills internal spaces

Connective tissue is a \________________ support to organs

structural

Examples of structures that have/are connective tissue

Bones, tendons, fat

What does muscle do?

contracts to cause movement, generates heat used to maintain core body temperature

Examples of muscles

skeletal, cardiac, smooth

What does nervous tissue do?

carries information from one part of the body to another through electrical impulses (internal communication)

Examples of nervous tissue

brain, spinal cord, nerves

What 3 general features tend to anchor cells together and stabilize tissues?

glycoproteins on cell surface, basement membrane, intercellular junctions

Glycoproteins on cell surface help anchor cells to....

one another

Basement membrane helps anchor cells to...

connective tissue

Intercellular junctions are \______________________ in the membrane

specializations

Name the 5 common types of cellular junctions

tight junctions, adherens junctions, desmosomes, hemidesmosomes, gap junctions

Describe tight junctions

the fusion of transmembrane proteins of adjacent cells in the intercellular space that circle the entire cell

What do tight junctions do?

helps cells adhere to all surrounding cell, prevents leakage of extracellular fluid, doesn't allow any space between adjacent cells

What are adherens junctions?

a dense protein layer of proteins on the inside of the plasma membrane that attaches both to membrane proteins and to cytoskeletal proteins

Which junction has a long, extended plaque?

adherens junction

In adherens junctions...

cadherins attach intracellularly to a plaque and extends through the plasma membrane and attach to cadherins from an adjacent cell

In adherens junctions, there are \_______________ \_______ that hold cells together so ET can be a strong membrane barrier

adhesion belts

What are desmosomes?

button shape plaque under plasma membrane with intermediate filaments extending through cytoplasm and attaching to desmosome on opposite side of cell

Desmosomes have...

cadherins

Desmosomes resist pulling of tissue which creates internal \_______________ in tissue

strength

Desmosomes are common in \____________ & \____________ muscle and \_______________

cardiac; smooth; skin

Hemidesmosomes are common in what tissue?

epithelial

The plaque of hemidesmosomes have...

transmembrane integrin proteins inserted, integrins attaching to laminins on outside of cell, and intermediate filaments

What do integrins do in hemidesmosomes?

anchor to plaque and extend through the membrane nd anchor proteins in basement membrane

What do intermediate filaments provide?

strength and stability to tissue

What are gap junctions?

communicating junctions where adjacent cells are close together

Gap junctions contain \___________ in the plasma membrane which form hollow cylinders called \_________________

connexins; connexons

What do gap junctions do?

allow passage of chemical substances like solutes between cells, allow ion flow to synchronize activity in cells

What are the two major categories of epithelial tissue?

covering and lining epithelium, glandular epithelium

What are some special characteristics of ET that distinguish it from other tissues?

high degree of cellularity, specialized cellular/lateral contacts, polarity, avascularity, presence of a basement membrane, has a nerve supply, high regenerative capability

What type of specialized lateral contacts are common in epithelium?

hemidesmosomes

What is meant when we describe epithelial tissue as demonstrating polarity?

Cells near apical surface are different than the ones nearer the basal surface

What is the function of the basement membrane?

Anchors and supports ET sheets, helps it resists stretching and tearing, defines epithelial boundary

What are the 2 layers of the basement membrane?

basal lamina and reticular lamina

What is the basal lamina?

a thin superficial layer secreted by the ET cells

What does the basal lamina do?

acts as selective filter between the blood and the ET, acts as scaffolding which epithelial cells can migrate to repair a wound

What is the reticular lamina?

a deeper layer made up of collagen fibers produced by the underlying CT

What does the reticular lamina do?

anchor the basal lamina to underlying CT and provides mechanical strength

Which layer of the basement membrane is produced by epithelial cells?

basal lamina

Which layer of the basement membrane is produced by fibroblasts in the CT?

reticular lamina

What are the general functions of covering and lining epithelium?

protection, absorption and secretion, filtration and excretion, surface transport, sensory functions

What are the primary functions of simple epithelium?

filtration and rapid diffusion

What are the primary functions of stratified epithelium?

protects underlying tissues in areas subjected to abrasion

What is a gland?

one or more ET cells specialized to produce and secrete a product called secretion

What are endocrine glands?

ductless glands that secrete hormones directly into the interstitial fluid surrounding the secreting cell which then enter the blood

What are exocrine glands?

glands that form a duct which transports secretions to the epithelial surface

Exocrine glands may be \______________ or \__________________

unicellular; multicellular

Unicellular glands secrete onto the

epithelial surface

Multicellular glands secrete product into a...

duct that opens on an epithelial surface

What are the body's only unicellular exocrine glands?

mucous cells and goblet cells

Mucous and goblet cells are found in...

epithelial linings of intestinal and respiratory tracts

Mucous and goblet cells produce...

mucin

What are the two basic structural components of multicellular exocrine glands?

epithelium-derived duct and secretory unit (acinus)

What is the difference between simple and compound exocrine glands?

Simple exocrine glands have an unbranched duct whereas compound exocrine glands have branched ducts

Tubular secretory portions of multicellular exocrine glands have...

secretory cells that form tubes

Alveolar secretory portions of multicellular exocrine glands have...

secretory cells that form small, flask-like sacs