Lecture # 16

The reproductive systems of all higher animals are
similar but there is great variation on the basic pattern.

Organs     Sex Cells    Tube/Duct
(gonads) (gametes)

testes      sperm        sperm duct

ovaries    eggs           oviduct

Fertilization in higher animals is internal,
occurring inside the body of the mother.

Going along with internal fertilization are:
1. Increased development of the reproductive ducts
2. development of accessory structures of
the reproductive system

Accessory structures are characteristic parts of
the reproductive system other than the gonads
and ducts themselves.

Accessory structures:
1. facilitate the transfer of sperm
2. make fertilization more likely to occur
3. provide an environment for development of the
zygote

Accessory structures have developed in close
association with the urinary system.

urogenital system

Accessory structures of male mammals:

1. Cowper’s glands, the prostate gland, and the
seminal vesicles

Seminal fluid contains:
A. mucus made of proteins
B. proteolytic enzymes
C. glucose and fructose
D. alkaline buffers
E. prostaglandins

2. scrotum
 
3. Specializations of the sperm duct:

seminiferous tubules

vas efferens

epididymis

vas deferens (which empties into the urethra)

4. penis

three corpora cavernosa

Accessory structures of female mammals:

1. follicle surrounding each egg 

ovulation 

2. Specializations of the oviduct:

ostium with cilia

fallopian tube

uterus

cervix

vagina

3. labia minora, labia majora and clitoris

During the sexually indifferent stage, the sex
of the embryo can NOT be determined by
external structures.

primordia (singular: primordium)

Homologues are structures that arise from the same
primordium.

Female                 Male 

ovaries                testes

labia majora     scrotum

labia minora  and clitoris       penis

Bartholin’s Glands         Cowper’s Glands

Fertilization occurs in the oviduct near the ovaries.

Events in fertilization:

A. sperm must penetrate through the outer layers
of the egg
B. nucleus of the egg must unite with the
nucleus of the sperm
C. fertilized egg must be activated

Eggs of higher animals produce chemical
substances that encourage fertilization:
A. cause sperm to stick to the egg
B. stimulate sperm to swim
C. prolong the viability of the sperm

Changes in the membrane and cytoplasm of the egg
prevent multiple fertilization

Parthenogenesis is the development of eggs
without fertilization.

Secondary sexual characteristics are
characteristic structures of males and females
other than the reproductive system.

Development of secondary sexual characteristics is
hormonally controlled.

Reproductive behavior is is associated with
courtship and mating.

Secondary sexual characteristics serve as
stimuli for reproductive behavior.

Reproductive behavior:

A. ensures that the sexes are brought together

B. ensures that mating occurs at the appropriate time

C. ensures that the young are cared for

Courtship behavior is associated with an
individual mating event.

mating dance, mating ritual, display of plumage

Courtship behavior:

A. decreases aggression

B. identifies members of the same species but
opposite sex

pheromones = sex attractants

seasonal breeding

Control of seasonal breeding:

A. internal

B. external
       photoperiod
       temperature
       rainfall
       tides and waves