Download BIO 218 F 2012 CH 28 Martini Lecture Outline

Biology 218 – Human Anatomy
Session:
FALL
Section:
52999
Days / Time:
Instructor:
Lecture Outline
MW 5:00 PM – 9:20 PM
RIDDELL
Adapted from Martini Human Anatomy 7th ed.
Chapter 28
The Reproductive System: Embryology and Human Development
Introduction
Development involves:
Differentiation of cells
Reorganization of cells
Development can be characterized by different periods of time
Prenatal development
Embryology
Postnatal development
An Overview of Development
Development can be characterized by different periods of time
Prenatal development
Conception to delivery
Involves embryology (development during the prenatal period)
Postnatal development
Development from birth to maturity
Fertilization
Fertilization is the joining of two haploid
cells to create a diploid cell
Function of the haploid cells
Spermatozoon
Delivers the paternal chromosomes to the ovum
Ovum
Provides the maternal chromosomes
Provides nourishment for embryonic development
Fertilization
Fertilization occurs in the ampulla of the uterine tube
200 million sperm cells enter the vaginal canal
Only about 10,000 make it to the uterine tubes
Less than 100 actually contact the egg
Only one will fertilize the egg
Fertilization
Fertilization details
When the egg is ovulated, it is surrounded by the corona radiata, which protects the egg as it is being
ovulated
Numerous sperm cells release hyaluronidase, from their acrosomal cap, in an effort to decompose the
corona radiata
Prenatal Development
Prenatal development is gestation period
(9 months)
© 2012 Pearson Education, Inc.
Page 1 of 12
840941469
Biology 218 – Human Anatomy
Session:
FALL
Section:
52999
Days / Time:
Instructor:
Lecture Outline
MW 5:00 PM – 9:20 PM
RIDDELL
Adapted from Martini Human Anatomy 7th ed.
Prenatal development is divided into trimesters
First trimester (rudiments of all organs appear)
Second trimester (fetus looks like a human)
Third trimester (organs become functional, rapid growth)
Prenatal Development
The First Trimester
1 to 12 weeks
Four events within the first trimester
Cleavage (sequence of cell reproduction)
Implantation (implantation into endometrial lining)
Placentation (formation of the placenta)
Embryogenesis (development of the embryo)
Prenatal Development
Cleavage and Blastocyst Formation
Cell division results in the formation of blastomeres
A solid ball of cells eventually develops – this is a morula
Some cells migrate to one “edge” of the morula creating a mass of cells and a hollow cavity called the
blastocoele
The ball of cells is now called the blastocyst
The outer layer of the blastocyst consists of cells called the trophoblast
Prenatal Development
Cleavage and Blastocyst Formation (continued)
Trophoblast cells provide nutrients to the developing embryo
The inner cell mass consists of stem cells that will develop into all the cells of the body
Prenatal Development
Implantation
Upon contact with the endometrial lining, the
trophoblast cells divide rapidly
The trophoblast cells “fuse” with the endometrial lining forming a syncytial trophoblast
This layer of cells releases hyaluronidase to erode away more of the endometrial lining so the mass can
implant
Prenatal Development
Implantation (continued)
Upon implantation, the inner cell mass separates from the trophoblast area
When the inner cell mass separates from the
trophoblast, two cavities form:
Amnionic cavity
Blastocoele cavity
Prenatal Development
Formation of the Blastodisc
© 2012 Pearson Education, Inc.
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840941469
Biology 218 – Human Anatomy
Session:
FALL
Section:
52999
Days / Time:
Instructor:
Lecture Outline
MW 5:00 PM – 9:20 PM
RIDDELL
Adapted from Martini Human Anatomy 7th ed.
A layer of cells forms between the amnionic cavity and the blastocoele cavity
The layers are called
Epiblast
Hypoblast
Prenatal Development
Gastrulation and Germ Layer Formation
Eventually some cells of the epiblast move toward the center of the blastodisc creating a primitive streak
This movement is called gastrulation
As the cells move toward the primitive streak area, they begin to migrate between the epiblast and
hypoblast layers
This creates three distinct layers of cells
Prenatal Development
Gastrulation and Germ Layer Formation
The three layers of cells are:
Ectoderm (derived from the epiblast layer)
Mesoderm (new layer between the epiblast and hypoblast)
Endoderm (derived from the hypoblast layer)
Prenatal Development
The ectoderm, mesoderm, and endoderm are collectively known as the germ layers
Each layer will form specific tissues and organs of the body
Germ layers will also form structures involved in embryonic survival called extraembryonic membranes
Prenatal Development
Formation of Extraembryonic Membranes
There are four major extraembryonic membranes
Yolk sac
Amnion
Allantois
Chorion
Prenatal Development
Formation of Extraembryonic Membranes
Yolk sac
This is a pouch that extends from the hypoblast cells into the blastocoele
It is the early site for blood cell formation
Amnion
Amnionic fluid fills the amnion cavity, which surrounds and cushions the embryo and fetus
Prenatal Development
Formation of Extraembryonic Membranes (continued)
Allantois
Eventually gives rise to the urinary bladder
Chorion
The mesoderm and trophoblast layers form together to form the chorion
The chorion will eventually develop extensions into the endometrium
© 2012 Pearson Education, Inc.
Page 3 of 12
840941469
Biology 218 – Human Anatomy
Session:
FALL
Section:
52999
Days / Time:
Instructor:
Lecture Outline
MW 5:00 PM – 9:20 PM
RIDDELL
Adapted from Martini Human Anatomy 7th ed.
Prenatal Development
Placentation
The placenta begins to form when the chorion
produces villi (chorionic villi) that extend into the endometrial lining
The body stalk connects the embryo to the chorion
As the fetus develops and moves farther into the uterus, it obtains its nutrients via the umbilical cord
Prenatal Development
Embryogenesis
Shortly after gastrulation, embryogenesis begins
By week 4, a head fold and tail fold develop
The embryo is separated from the blastodisc area
Prenatal Development
Embryogenesis
At about 12 weeks, organs begin to form
This is called organogenesis
Prenatal Development
Second Trimester
Fetus is covered by the amnion sac
Fetus grows faster than the placenta
Third Trimester
All fetal organs become functional
Prenatal Development
Changes in the uterus during gestation
Uterus will increase in length from 7.5 cm to 30 cm
Contains almost 5 L of fluid
The uterus and contents weigh about 22 pounds
Abdominal organs are pushed out of their normal positions
Labor and Delivery
The goal of labor is parturition (expulsion of the fetus)
There are three stages of labor
Dilation stage
Expulsion stage
Placental stage
Labor and Delivery
The dilation stage
The fetus begins to move down the cervical canal
The cervix dilates
The amnion sac breaks
The expulsion stage
The birth of the child
The placental stage
Ejection of the placenta
© 2012 Pearson Education, Inc.
Page 4 of 12
840941469
Biology 218 – Human Anatomy
Session:
FALL
Section:
52999
Days / Time:
Instructor:
Lecture Outline
MW 5:00 PM – 9:20 PM
RIDDELL
Adapted from Martini Human Anatomy 7th ed.
The Neonatal Period
This is the period from birth to one month
Events that occur from birth to one month are:
Lungs fill with air
Blood circulation changes with the closing of the ductus arteriosus and the foramen ovale of the heart
Heart rate drops from 120–140 beats per minute to about 70
Breathing rate drops from 30 per minute to the
normal rate
The Neonatal Period
Events that occur from birth to one month are (continued):
Kidneys filter the infant’s own blood
Digestive system becomes active
Metabolic rate is increased to maintain warmth for a few days after birth
Embryology Summary
Overview of Embryology
The development of the:
Integumentary System
Skull
Vertebral Column
Appendicular Skeleton
Muscles
Nervous System
Spinal Cord
Brain
Special Sense Organs
Embryology Summary
The Development of the Integumentary System
1 month: epithelium overlies mesenchyme
3 months: epithelium multiplies to form layers;
mesenchyme develops into connective tissue thus forming the dermis
4 months: epidermis begins to grow into the dermis thus forming columns of cells;
hair follicles, sweat glands, and sebaceous glands develop from these columns
Embryology Summary
The Development of the Integumentary System (continued)
Skin: at 3 months, the epithelium continues to
thicken
Melanocytes migrate into the stratum basale layer
Nails: develop from the thickening of the epidermis
© 2012 Pearson Education, Inc.
Page 5 of 12
840941469
Biology 218 – Human Anatomy
Session:
FALL
Section:
52999
Days / Time:
Instructor:
Lecture Outline
MW 5:00 PM – 9:20 PM
RIDDELL
Adapted from Martini Human Anatomy 7th ed.
Embryology Summary
The Development of the Skull
5 weeks
Cartilage begins to appear
Cartilage within the brain area enlarges to form the
chondrocranium
Skull walls and floor are beginning but no roof
9 weeks
Endochondral ossification appears; frontal and parietal structures appear
Embryology Summary
The Development of the Skull (continued)
10 weeks
Mandibular arch fuses with the chondrocranium
Hyoid arch begins to form
12 weeks
Ossification is well under way
Birth
Cranial roof remains incomplete
The anterior and posterior fontanels are present
Embryology Summary
The Development of the Vertebral Column
4 weeks
On either side of the developing spinal cord are blocks of mesenchymal tissue called somites
The medial side of the somites produces the vertebral column
8 weeks
Vertebral cartilage forms around the spinal cord
The sacrum and coccyx are fused together
Embryology Summary
The Development of the Vertebral Column (continued)
12 weeks
Ribs and sternum undergo ossification
The tips of the longer ribs do not ossify; they remain
as cartilage thus forming the costal cartilages
Embryology Summary
The Development of the Appendicular Skeleton
4 weeks
Ridges appear along the length of the embryo
An accumulation of ridges at the superior end and the inferior end form pairs of limb buds
5 weeks
Limb buds develop a core of cartilaginous tissue
Cartilaginous models develop between 5 and 8 weeks
10 weeks
© 2012 Pearson Education, Inc.
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840941469
Biology 218 – Human Anatomy
Session:
FALL
Section:
52999
Days / Time:
Instructor:
Lecture Outline
MW 5:00 PM – 9:20 PM
RIDDELL
Adapted from Martini Human Anatomy 7th ed.
Ossification occurs
Embryology Summary
The Development of Muscles
4 weeks
Mesoderm on either side of the notochord forms somites
The medial portion of each somite forms skeletal
muscles; this region is called the myotome
6 weeks
Myotome area develops into posterior muscles called epaxial muscles and anterior muscles called
hypaxial muscles
Embryology Summary
The Development of Muscles (continued)
7 weeks: muscles of the face, back, and abdomen develop
8 weeks: limbs enlarge and muscles continue to develop
Embryology Summary
The Development of the Nervous System
2 weeks
Somites appear on either side of the notochord
A neural plate is formed
A crease develops along the length of the neural plate
The edges of the crease are the neural folds
The neural folds “fold” to form a tube (neural tube)
3 weeks
The neural tube becomes the CNS
Axons extending from the neural tube become the PNS
Embryology Summary
The Development of the Spinal Cord
22 days
The neural tube is closed thus producing
three layers:
Ependymal layer
Mantle layer
Marginal layer
Neurons develop in the mantle layer
Axons grow from the mantle layer to the marginal
layer
Embryology Summary
The Development of the Spinal Cord (continued)
23 days
Axons form bundles and tracts in the spinal cord
© 2012 Pearson Education, Inc.
Page 7 of 12
840941469
Biology 218 – Human Anatomy
Session:
FALL
Section:
52999
Days / Time:
Instructor:
Lecture Outline
MW 5:00 PM – 9:20 PM
RIDDELL
Adapted from Martini Human Anatomy 7th ed.
7 weeks
Ventral roots and dorsal roots develop
Glial cells develop
Spinal and cranial meninges develop
Spinal nerves develop
Embryology Summary
The Development of the Brain
23 days
The cephalic extension forms three brain vesicles
Prosencephalon
Mesencephalon
Rhombencephalon
Embryology Summary
The Development of the Brain (continued)
4 weeks
The rhombencephalon subdivides to form:
Metencephalon
Myelencephalon
The prosencephalon subdivides to form:
Telencephalon
Diencephalon
Embryology Summary
The Development of the Brain (continued)
5 weeks
Mesencephalon develops
Cranial nerves begin to develop
8 weeks
Choroid plexus develops
Cerebral hemispheres expand
11 weeks
Cerebellum develops
Embryology Summary
The Development of Special Sense Organs
4 weeks
Optic bulges appear in the lateral walls of the prosencephalon
The bulges indent forming the optic cup
The epidermis covering the optic cup forms the lens
5 weeks
A pair of thickened areas in the front of the prosencephalon form the olfactory receptors
When nerves innervate the tongue, the epithelial cells differentiate to form gustatory cells
Embryology Summary
The Development of Special Sense Organs (continued)
© 2012 Pearson Education, Inc.
Page 8 of 12
840941469
Biology 218 – Human Anatomy
Lecture Outline
Session:
FALL
Section:
52999
Days / Time:
Instructor:
MW 5:00 PM – 9:20 PM
RIDDELL
Adapted from Martini Human Anatomy 7th ed.
3 weeks
Otic regions begin to appear on the lateral sides of the rhombencephalon
4 weeks
Deep pockets form in the otic regions, creating otic vesicles
6 weeks
The vesicles form the bony labyrinth
This process continues until the end of the third month
Embryology Summary
The Development of the Endocrine System
Week 5
Five pharyngeal pouches are formed
The pouches form the thymus gland, parathyroid
gland, and thyroid gland
The pituitary gland forms as a pocket in the pharyngeal area; this ectodermal pocket breaks away from
the pharyngeal area and develops just superior to the thyroid gland area
Embryology Summary
The Development of the Endocrine System
Week 5 (continued)
After the formation of the neural tube, some neural cells migrate away from the CNS and form an
aggregate of cells that become the suprarenal glands
Embryology Summary
The Development of the Heart
Week 2
The heart begins as a pair of tubes in the pharynx area
Week 3
The heart begins to pump
The tubes fuse forming a one-chambered heart
Two large veins bring blood to the heart
One large artery carries blood away from the heart; the artery is called the truncus arteriosus
Embryology Summary
The Development of the Heart (continued)
Week 5
The interatrial and interventricular septa begin to form, ultimately forming the four chambers of the heart
The foramen ovale and ductus arteriosum form
1 year
The foramen ovale and ductus arteriosum have closed (at birth)
The remnant of the foramen ovale is the fossa ovalis
The remnant of the ductus arteriosum is the ductus
ligamentum
Embryology Summary
© 2012 Pearson Education, Inc.
Page 9 of 12
840941469
Biology 218 – Human Anatomy
Lecture Outline
Session:
FALL
Section:
52999
MW 5:00 PM – 9:20 PM
Days / Time:
Instructor:
RIDDELL
Adapted from Martini Human Anatomy 7th ed.
The Development of the Cardiovascular System
Week 4
Several aortic arches form and fuse together to form the dorsal aorta
Some of the aortic arches disintegrate leaving ultimately just one aortic arch
Embryology Summary
The Development of the Cardiovascular System
Week 4 (continued)
Venous circulation begins with the following vessels draining the tissues:
Anterior cardinal veins
Posterior cardinal veins
Subcardinal veins
These veins are paired and each pair fuses to form:
Superior vena cava
Inferior vena cava
Embryology Summary
The Development of the Cardiovascular System
Week 4 (continued)
Umbilical arteries carry blood to the placenta
Umbilical veins carry blood to the liver
Week 12
Right umbilical vein disintegrates
Ductus venosus allows some blood to bypass the liver
Veins draining the digestive tract fuse to form the hepatic portal vein
Embryology Summary
The Development of the Lymphoid System
Week 7
The thymus gland forms from a pharyngeal pouch
The cells lose their attachment and form just inferior to the thyroid gland area
Week 8
Numerous lymphatic sacs form throughout the body
Embryology Summary
The Development of the Respiratory System
Week 3
A pulmonary groove forms in the pharynx area
Week 4
This groove forms deeper and then forms two blind pouches at the end of the groove
The groove forms a tube, which becomes the trachea, and the two blind pouches become the lungs
Week 9
The diaphragm forms
Embryology Summary
© 2012 Pearson Education, Inc.
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840941469
Biology 218 – Human Anatomy
Session:
FALL
Section:
52999
Days / Time:
Instructor:
Lecture Outline
MW 5:00 PM – 9:20 PM
RIDDELL
Adapted from Martini Human Anatomy 7th ed.
The Development of the Respiratory System (continued)
3 Months
The lung buds continue to branch numerous times
6 Months
There are a million branches
All the bronchioles are formed
6–9 Months
Alveoli begin to form
Embryology Summary
The Development of the Digestive System
Week 3
Yolk sac is formed
The layer between the yolk sac and the amniotic sac develops a hindgut and a foregut
The hindgut and the foregut form the digestive tube
Week 4
Lateral to the digestive tube are cavities called the coelomic cavities
The digestive tube is held in position within the midline of the coelomic cavities by the dorsal mesentery
and ventral mesentery
Embryology Summary
The Development of the Digestive System
Week 4 (continued)
The pancreas is formed within the dorsal mesentery area
The liver is formed within the ventral mesentery area
Part of the ventral mesentery becomes the falciform ligament of the liver
The remaining mesenteric tissue becomes the greater omentum and lesser omentum
Embryology Summary
The Development of the Digestive System (continued)
Week 6
The intestines elongate and coil
The yolk sac and the body stalk fuse to form the
umbilical cord
Embryology Summary
The Development of the Urinary System
Week 3.5
The kidneys begin as seven pairs of tubules called pronephric tubes
Week 6
Branches of the aorta extend toward the pronephric tubes
Week 8
The allantois becomes the urinary bladder
Week 12
Kidneys begin producing filtrate even though there aren’t any waste products in it
© 2012 Pearson Education, Inc.
Page 11 of 12
840941469
Biology 218 – Human Anatomy
Session:
FALL
Section:
52999
Days / Time:
Instructor:
Lecture Outline
MW 5:00 PM – 9:20 PM
RIDDELL
Adapted from Martini Human Anatomy 7th ed.
Embryology Summary
The Development of the Reproductive System
Weeks 3–6
Endodermal cells of the yolk sac migrate to the genital ridges in the abdominal cavity
Each ridge consists of columns of cells called primary sex cords; these will further develop into gonads
Embryology Summary
The Development of the Reproductive System
Weeks 3–6 (continued)
If the gonad-developing cells are exposed to androgens, a male will develop, regardless of the genetic
sex of the embryo
If they are not exposed to androgens, a female will
develop, regardless of the genetic sex of the embryo
The male embryo will begin producing testosterone after week 6, which then directs the development of
the external genitalia
Embryology Summary
Development of the Male Reproductive System
Week 7
The primary sex cords proliferate and eventually form the seminiferous tubules within the developing
testes
Week 10
The urethral folds begin to fuse to form the spongy urethra of the penis
This line of fusion can be seen in the adult as the raphe
7 Months
The testes descend into the scrotum
Embryology Summary
Development of the Female Reproductive System
Weeks 7–12
Primary sex cords degenerate
Primordial germ cells migrate to the genital ridge
The urethral folds do not fuse; they become the labia
minora
Week 10
The ovaries and uterus develop
© 2012 Pearson Education, Inc.
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840941469