Tissues Flashcards
Identify the stages of pre-embryonic development, beginning at fertilization and ending
at gastrulation. Describe the main event(s) of each stage.
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Cleavage (Days 1-3) - this period of rapid biotic cell division 24 hours after fertilization forms blastomeres then morulas until day 4
Blastocyst - (Day 4 - 7)
When the morula hollows out and creates a cavity with a cluster on one side (contains 32 cells exactly called the embryoblast) and outlined with the trophoblast
Implantation - Trophoblast cells secrete enzymes which breaks down its covering (zone pellucida) and the blastocyst hatches. (forms 2 layers and becomes the embryonic disc)
- By day 7-8 it embeds to the uterine wall. hCG and luteinizing hormone help maintain the uterine lining.
- The bilaminar embryonic disc develops into the embryo and the separation between the epiblast and hypoblast fills with amniotic fluid.
Gastrulation - Formation of primary tissues.
- Embryonic disc forms primitive streak which forms dorsal of fetus and marks the tail.
- bilaminar embryonic disk forms three layers.
What is a blastomere?
identical cells formed by cleavage divisions
Describe the histological differences between a morula and a blastocyst.
The morula doesnt have the blastocyst cavity and trophoblast outlining it. It is a solid mans.
What are the two distinct cellular components of a blastocyst?
Trophoblast - the singular layer of large flattened cells with the blastocyst
Embryoblast- cluster of 20-30 cells within the blastocyst. (above the blastocyst cavity)
What is the function of the trophoblast?
Help invade uterine wall
Secrete enzymes that break down the zone pellucida (the covering around the blastocyst that was there since the egg was fertilized.)
secretes hCG
forms the cellular trophoblast (inner layer, looks like a membrane.) and syncytial trophoblast (outer layer that forms a slime looking thing.)
What role does human chorionic gonadotropin (hCG) play in sustaining pregnancy?
How has knowledge of this hormone become clinically and commercially useful?
Prevents the mothers immune system from rejecting the implanted embryo. It helps maintain the uterine lining to support the development of the embryo.
All pregnancy tests used today are antibody tests that detect hCG in a woman’s blood or urine.
From what embryonic structure does the bilaminar embryonic disk originate?
embryoblast ; the epiblast and hypoblast
Identify the three primary germ layers and describe which tissues ultimately derive from
each.
(Outer layer) Ectoderm -
Skin cells, neurons, pigment cells
Systems: Nervous system and skin epidermis
(Middle layer) Mesoderm -
Cardiac muscle cells, skeletal muscle cells, tubule cells of the kidney, red blood cells, smooth muscle cells
Systems: Mainly connective tissue cells and created organs of the urogenital systems
(Inner layer) Endoderm -
Lung cells, thyroid cells, digestive cells (pancreatic cell)
Systems: Epithelial linings of digestive tract, respiratory and urogenital and glands
Identify the four extraembryonic membranes and describe the function of each.
the amnion- develops sac that surrounds the amniotic cavity (which is filled with amniotic fluid.)
the yolk sac - main source of nutrition for the embryo, forms part of the gut, earliest source off blood cells, where germ cells migrate to form sperm and ova
allantois- structural base for the umbilical cord that links the embryo to the placenta and eventually becomes the bladder.
chorion - helps form the placenta and as the outermost membrane, encodes the embryonic body and all other membranes
What is a tissue?
groups of similar cells that are specialized to perform a particular function
Identify and describe the general function of each of the four basic tissue types.
Eric Makes Cassandra Nervous
Epithelial- Forms boundaries between different environments, protects, secretes and absorbs.
Muscular - Contracts to cause movement
Connective- Supports, protects, binds, other tissues together
Nervous- Internal Communication
What three general features tend to anchor cells together and stabilize tissues?
BCG
Basement membrane
Cell junctions
Glycoproteins
Describe the structure and function of each of the five common types of cellular
junctions.
TAG @ DH
Tight junctions- Adjacent (side by side cells) fused by transmembrane proteins.
*Prevent leakage, are in epithelium cells (respiratory tract)
Adherens- Has an adhesion belt made of plaque and tied together by cadherins. Attached to membrane proteins and microfilaments of the cytoskeleton.
*Adhesion belt prevents separation of epithelial surfaces (allows epithelium to form a covering)
Gap junctions- Connected by connexions but theres gaps between the cells.
- Allows the passage of chemical substances. Helps ions like sugar pass (distributes nutrients to fetuses before the circulatory system is created.)
- Important in smooth muscle, heart, epithelial.
Desesomes- Is like Adherens but the plaque is circular and they have intermediate filaments sticking out
- Helps distribute tension among skin, cardiac muscles, smooth muscle, neck region of the uterus
- Provides strength and stress points
Hemidesmosomes- Looks like Desesomes but is only half of it. Has interns that attach tho the basement membrane. NOT INTERCELLULAR (doesnt bind to another cell)
Identify the two major categories of epithelial tissue.
Glands
Covering and Lining Epithelium
What 5 special characteristics of epithelial tissue distinguish it from other tissue types?
- High degree of cellularity (can multiple fast)
- Specialized cellular contacts
(cellular junctions) - Polarity
(It has an apical side and a lumen side that faces the cavity of the internal organ) - Avascular
(no blood vessels, but has nerve supply) - Has a basement membrane
(Basal lamina - thin layer, is a filter between the blood and ET but allows nutrients to pass through.)
(Reticular lamina- Deeper layer of fibroblast/collagen fibers CT)
What type(s) of specialized lateral contacts are common in epithelium?
tight junctions and desmosomes
What are the 4 general functions of covering and lining epithelium?
- Protection
- Controls permeability
* Absorption & secretion
- Filtration & excretion
3. Surface transport (cilia)
4. Sensory Function
What are the primary functions of simple epithelium? of stratified epithelium?
absorption and filtration processes ; protection
What is a gland?
One or more specialized ET to produce and secrete secretion
Distinguish between endocrine and exocrine glands.
Endocrine - secretes HORMONES into the interstitial fluid (fluid around cells) around secreting cells
Exocrine- secretes PRODUCT into a duct that carries their produce to the surface (skin)
Multicellular - secretes product into a duct that open on an epithelia surface (liver produces bile, salivary glands, pancreas)
Unicellular-(goblet cells and mucous cells) secretes mucins that mixes with water to create mucus ; secrete on epithelia surfaces.
Identify, locate, and describe the function of the human body’s only unicellular
exocrine gland.
Goblet cells, in the epithelial linings of the intestinal and respiratory tracts , secretes mucin which makes mucous
What are the two basic structural components of multicellular exocrine glands?
A duct and a secretory unit (consisting of secretory cells)
What is the difference between simple and compound exocrine glands?
Simple - have an unbranched duct
Compound - Have a branched duct
What is the difference between the tubular, alveolar, and tubuloalveolar secretory
portions of multicellular exocrine glands?
Tubular - secretory cells form tubes
Alveolar- Secretory cells form small hollow cavities
Tubloalveolar - both
Name the three functional types of exocrine gland and describe the secretory process of each.
MAH
Merocine gland - Most common, secrete by exocytosis, cell is not damaged bt it
Apocrine gland - Accumulate secretory product near the apical surface and end up pinching that apical region off
Holocrine gland - explodes when it builds up with secretory product
Which of the above gland types (#30) is most common in the body?
Meocrine
What is the most abundant tissue in the human body?
Connective Tissue